Continuously variable transmission apparatus

ABSTRACT

A continuously variable transmission apparatus has clutch device having a low speed clutch; a high speed clutch; and, a controller switching the transmission state into any one of a low speed mode and a high speed mode by connecting any one of the clutches, wherein timings for signaling by the controller for switching the connected and disconnected states of the clutches vary according to the switching directions of the low speed and high speed modes; and, a timing for signaling for connecting the low speed clutch with respect to the moment for signaling for cutting off the connection of the high speed clutch in order to switch the high speed mode over to the low speed mode is set earlier than a timing for signaling for connecting the high speed clutch with respect to the moment for signaling for cutting off the connection of the low speed clutch.

BACKGROUND OF THE INVENTION

1. Field of the invention

A continuously variable transmission apparatus according to the presentinvention is used as a transmission unit constituting an automatictransmission for a vehicle or as a transmission for any one of variouskinds of industrial mechanical apparatus. Especially, a continuouslyvariable transmission apparatus according to the present invention isdeveloped in order to reduce an incongruous feeling given to a driverwhen switching a low speed mode and a high speed mode over to each otherusing a clutch mechanism.

2. Description of the Related Art

As an automatic transmission for a vehicle, such a toroidal-typecontinuously variable transmission as schematically shown in FIGS. 10and 11 is known well because it is disclosed in many publications suchas patent publications, and it is also enforced currently in part of thevehicle industry. When a toroidal-type continuously variabletransmission of this type is in operation, as an input shaft 1 isrotated, a pressing device 2 such as a loading cam rotates an input sidedisk 3 while pressing the input side disk 3 against a plurality of powerrollers 4, 4. And, the rotational power of the input side disk 3 istransmitted through the plurality of power rollers 4, 4 to an outputside disk 5, so that an output shaft 6 fixed to the output side disk 5is rotated.

To change the rotation speed between the input shaft 1 and output shaft6, trunnions 7, 7 supporting the power rollers 4, 4 thereon arerespectively swung about their associated pivot shafts 8, 8 which aredisposed on the two end portions of each of the trunnions 7, 7 in such amanner that the pivot shafts 8, 8 are respectively concentric with theirassociated trunnions 7, 7. In this case, in case where the rotationcenter axes of the power rollers 4, 4 are swung in such a manner thatthe peripheral surfaces 4 a, 4 a of the power rollers 4, 4, as shown inFIG. 10, can be respectively contacted with the near-to-center portionof the inner surface 3 a of the input side disk 3 and thenear-to-outer-periphery portion of the inner surface 5 a of the outputside disk 5, the rotation speed between the input shaft 1 and outputshaft 6 can be reduced. On the other hand, in case where the rotationcenter axes of the power rollers 4, 4 are swung in such a manner thatthe peripheral surfaces 4 a, 4 a of the power rollers 4, 4, as shown inFIG. 11, can be respectively contacted with the near-to-outer-peripheryportion of the inner surface 3 a of the input side disk 3 and thenear-to-center portion of the inner surface 5 a of the output side disk5, the rotation speed between the input shaft 1 and output shaft 6 canbe increased.

While the basic structure of a toroidal-type continuously variabletransmission is as described above, to swing the trunnions 7, 7 abouttheir respective pivot shafts 8, 8 in order to change the transmissionratio, the trunnions 7, 7 may be shifted slightly in the axial direction(in FIGS. 10 and 11, in the front and rear direction of the sheets ofFIGS. 10 and 11) of the pivot shafts 8, 8. As the trunnions 7, 7 areshifted in this manner, the direction of a force to be applied to therolling contact portions between the above-mentioned surfaces 3 a, 4 aand 5 a in the tangential direction thereof is caused to vary, with theresult that trunnions 7, 7 can be swung. The structure of this portionis also well known because it is disclosed in many publications such aspatent publications, and the present structure is currently enforced inpart of the vehicle industry. Also, structures, each of which is used toincrease the number of power rollers for use in power transmission tothereby be able to increase the power that can be transmitted by thetoroidal-type continuously variable transmission, are also disclosed inmany publications such as patent publications and thus are known well;and, part of these structures are now practically applied. As suchstructures for increasing the number of power rollers in this manner,for example, there are widely known a structure in which two pairs ofinput side and output side disks are disposed in parallel to each otherwith respect to the transmission direction of the power, and a structurein which the number of power rollers to be interposed between the inputside and output side disks can be increased.

Further, as disclosed in JP-A-1-169169, JP-A-1-312266, JP-A-10-196759,JP-A-11-63146, JP-A-11-63148, and JP-A-2000-220719, conventionally,there is also proposed a structure in which a toroidal-type continuouslyvariable transmission and a planetary gear transmission mechanism arecombined together to thereby construct a continuously variabletransmission apparatus. The present continuously variable transmissionapparatus is invented so as to increase the width of the transmissionratio; or, to reduce the torque that passes through the toroidal-typecontinuously variable transmission when a vehicle is running at a highspeed, thereby being able to enhance the durability of the toroidal-typecontinuously variable transmission; or, to allow a continuously variabletransmission by itself to stop the output shaft even during the rotationof the input shaft, thereby being able to eliminate the need forprovision of a start clutch.

Now, FIG. 12 shows an example of a conventional continuously variabletransmission apparatus of the above-mentioned type which is disclosed inthe above-cited JP-A-11-63146. This continuously variable transmissionapparatus comprises a double cavity type of toroidal-type continuouslyvariable transmission 9 and a planetary gear mechanism 10; and,specifically, in the toroidal-type continuously variable transmission 9,two pairs of input side and output side disks are disposed in parallelto each other with respect to the power transmission direction. And,according to this continuously variable transmission apparatus, in thelow speed running operation, the power is transmitted only by thetoroidal-type continuously variable transmission 9; and, in the highspeed running operation, the power is transmitted mainly by theplanetary gear mechanism 10 and, at the same time, the transmissionratio given by the planetary gear mechanism 10 can be adjusted bychanging the transmission ratio of the toroidal-type continuouslyvariable transmission 9.

For the above purpose, the base end portion (in FIG. 12, the right endportion) of an input shaft 1 a passing through a centrosphere of thetoroidal-type continuously variable transmission 9 and supporting a pairof input side disks 3, 3 on the two end portions thereof is connected toa transmission shaft 13, which is fixed to the central portion of asupport plate 12 supporting a ring gear 11 constituting the planetarygear mechanism 10, by a high speed clutch 14. By the way, of the pair ofinput side disks 3, 3, the input side disk 3 disposed on the leading endside (in FIG. 12, the right side) of the input shaft 1 a is supported onthe input shaft 1 a in such a manner that it is rotatable insynchronization with the input shaft 1 a as well as it is preventedagainst substantial movement in the axial direction of the input shaft 1a. On the other hand, the input disk 3 on the base end side (in FIG. 12,the left side) is supported on the input shaft 1 a in such a manner thatit can be rotated in synchronization with the input shaft 1 a as well ascan be moved in the axial direction of the input shaft 1 a.

Also, between the output side end portion (in FIG. 12, the right endportion) of a crankshaft 16 of an engine 15 serving as a drive sourceand the input side end portion (that is, the base end portion; in FIG.12, the left end portion) of the input shaft 1 a, there are interposed astart clutch 17 such as a torque converter or an electromagnetic clutchand an oil pressure type of pressing device 18 in such a manner thatthey are connected in series with each other with respect to the powertransmission direction. This pressing device 18 is structured byinserting the base end portion of the input disk 3 into a cylinder 19 insuch a manner that the input disk 3 is oiltight and is able to transmitthe rotational power thereof.

Also, an output shaft 20, which is used to take out the power based onthe rotational motion of the input shaft 1 a, is disposed so as to beconcentric with the input shaft 1 a. And, on the periphery of the outputshaft 20, there is disposed the planetary gear mechanism 10. A sun gear21, which constitutes the planetary gear mechanism 10, is fixed to theinput side end portion (in FIG. 12, the left end portion) of the outputshaft 20. Therefore, the output shaft 20 can be rotated as the sun gear21 is rotated. On the periphery of the sun gear 21, there is supportedthe ring gear 11 in such a manner that it is concentric with the sungear 21 and can be rotated. And, between the inner peripheral surface ofthe ring gear 11 and the outer peripheral surface of the sun gear 21,there are interposed a plurality of planetary gear sets 23, 23 each ofwhich comprises a pair of planetary gears 22 a and 22 b combinedtogether. Each pair of planetary gears 22 a and 22 b are meshinglyengaged with each other; and, the planetary gear 22 a disposed on theoutside diameter side is meshingly engaged with the ring gear 11, whilethe planetary gear 22 b disposed on the inside diameter side ismeshingly engaged with the sun gear 21. The thus arranged planetary gearsets 23, 23 are rotatably supported on one side surface (in FIG. 12, theleft side surface) of a carrier 24. Also, the carrier 24 is rotatablysupported on the middle portion of the output shaft 20.

And, the carrier 24 is connected to a pair of output side disks 5, 5constituting the toroidal-type continuously variable transmission 9 by afirst power transmission mechanism 25 in such a manner that therotational power can be transmitted between them. The first powertransmission mechanism 25 comprises a transmission shaft 26 disposed soas to extend in parallel to the input shaft 1 a and output shaft 20, asprocket 27 a fixed to one end portion (in FIG. 12, the left endportion) of the transmission shaft 26, a sprocket 27 b connected to therespective output disks 5, 5, a chain 28 interposed across the twosprockets 27 a and 27 b, and first and second gears 29, 30 which arerespectively fixed to the other end (in FIG. 12, the right end) of thetransmission shaft 26 and the carrier 24 and are meshingly engaged witheach other. Thanks to this, as the respective output side disks 5, 5 arerotated, the carrier 24 can be rotated in the opposite direction to theoutput side disks 5, 5 at the speed that corresponds not only to thenumber of teeth of the first and second gears 29, 30 but also to thenumber of teeth of the pair of sprockets 27 a, 27 b.

On the other hand, the input shaft 1 a can be connected to the ring gear11 through another transmission shaft 13, which is disposedconcentrically with the input shaft 1 a and serves as a secondtransmission mechanism, in such a manner that the rotational power canbe transmitted between them. Between this transmission shaft 13 andinput shaft 1 a, there is interposed the high speed clutch 14 in such amanner that it is arranged in series with the two shafts 13 and 1 a.Therefore, the transmission 13, when the high speed clutch 14 isconnected, can be rotated together with the input shaft 1 a in the samedirection and at the same speed.

Also, the present continuously variable transmission apparatus comprisesthe high speed clutch 14 and a low speed clutch 31 interposed betweenthe outer peripheral edge portion of the carrier 24 and theaxial-direction one end portion (in FIG. 12, the right end portion) ofthe ring gear 11. The low speed clutch 31 and high speed clutch 14 arestructured such that, in case where any one of these clutches isconnected, the connection of the other clutch is cut off. Also, in theexample shown in FIG. 12, between the ring gear 11 and the fixed portionof the present continuously variable transmission apparatus such as ahousing (not shown), there is interposed a reversing clutch 32. In casewhere any one of the low speed clutch 31 and high speed clutch 14 isconnected, the connection of the reversing clutch 32 is cut off. Also,in case where the reversing clutch 32 is connected, the low speed clutch31 and high speed clutch 14 are both disconnected.

In the case of the above structured continuously variable transmissionapparatus, firstly, during the low speed running operation, the lowspeed clutch 31 is connected and, at the same time, the high speedclutch 14 and reversing clutch 32 are disconnected respectively. In thisstate, in case where the start clutch 17 is connected and the inputshaft 1 a is rotated, only the toroidal-type continuously variabletransmission 9 is allowed to transmit the power from the input shaft 1 ato the output shaft 20. In such low speed running operation, thetransmission ratios between respective pairs of input side disks 3, 3and output side disks 5, 5 are adjusted similarly to the case previouslyshown in FIGS. 10 and 11 in which only the toroidal-type continuouslyvariable transmission 9 is allowed to transmit the power.

On the other hand, in the high speed running operation, the high speedclutch 14 is connected and, at the same time, the connection of the lowspeed clutch 31 and reversing clutch 32 is cut off. In this state, incase where the start clutch 17 is connected and the input shaft 1 a isrotated, the transmission shaft 13 and planetary gear mechanism 10 areallowed to transmit the power from the input shaft 1 a to the outputshaft 20. That is, in case where the input shaft 1 a is rotated in thehigh speed running operation, the rotational power of the input shaft 1a is transmitted through the high speed clutch 14 and transmission shaft13 to the ring gear 11. And, the rotational power of the ring gear 11 istransmitted through the plurality of planetary gear sets 23, 23 to thesun gear 21, thereby rotating the output shaft 20 to which the sun gear21 is fixed. In this state, in case where the transmission ratio of thetoroidal-type continuously variable transmission 9 is changed to therebyvary the revolving speeds (the rotation speeds around the periphery ofthe sun gear 21) of the respective planetary gear sets 23, 23, thetransmission ratio of the whole of the continuously variabletransmission apparatus can be adjusted.

In other words, in case where the input shaft 1 a is rotated in the highspeed running operation, the rotational power of the input shaft 1 a istransmitted through the transmission shaft 13 and support plate 12 tothe ring gear 11, thereby rotating the ring gear 11. And, the rotationalpower of the ring gear 11 is then transmitted through the plurality ofplanetary gear sets 23, 23 to the sun gear 21, thereby rotating theoutput shaft 20 to which the sun gear 21 is fixed. When the ring gear 11serves as the input side, assuming that the respective planetary gearsets 23, 23 are not rotating (that is, they are not revolving around theperiphery of the sun gear 21), the planetary gear mechanism 10 increasesthe revolving speed between the input shaft 1 a and the output shaft 20by the transmission ratio that corresponds to the ratio of the numbersof the ring gear 11 and sun gear 21. However, the respective planetarygear sets 23, 23 actually rotate around the periphery of the sun gear21, while the transmission ratio of the whole of the continuouslyvariable transmission apparatus varies according to the speed of therotation (around the periphery of the sun gear 21) of the respectiveplanetary gear sets 23, 23. Thus, in case where the transmission ratioof the toroidal-type continuously variable transmission 9 is changed tothereby change the revolving speed (the rotation speed around theperiphery of the sun gear 21) of the respective planetary gear sets 23,23, the transmission ratio of the whole of the continuously variabletransmission apparatus can be adjusted.

That is, in the above-mentioned high speed running operation, therespective planetary gear sets 23, 23 rotate around the periphery of thesun gear 21 in the same direction of the ring gear 11. And, the slowerthe rotation speed (around the periphery of the sun gear 21) of therespective planetary gear sets 23, 23 is, the faster the rotation speedof the output gear 20 with the sun gear 21 fixed thereto is. Forexample, in case where the rotation speed (around the periphery of thesun gear 21) of the respective planetary gear sets 23, 23 is equal tothe rotation speed of the ring gear 11 (both of which are angularspeeds), the rotation speed of the ring gear 11 is equal to that of theoutput shaft 20. On the other hand, in case where the rotation speed(around the periphery of the sun gear 21) of the respective planetarygear sets 23, 23 is faster than the rotation speed of the ring gear 11,the rotation speed of the output shaft 20 is slower than that of thering gear 11.

Therefore, in the high speed running operation, as the transmissionratio of the toroidal-type continuously variable transmission 9 ischanged toward the speed reducing side, the transmission ratio of thewhole of the continuously variable transmission apparatus is changedtoward the speed increasing side. In the state of such high speedrunning operation, to the toroidal-type continuously variabletransmission 9, there is applied torque not from the input side disk 3but from the output side disk 5 (that is, assuming that torque to beapplied in the low speed running operation is positive, negative torqueis applied). In other words, in a state where the high speed clutch 14is connected, the torque, which has been transmitted from the engine 15to the input shaft 1 a, is then transmitted through the transmissionshaft 13 to the ring gear 11 of the planetary gear mechanism 10.Therefore, there remains little torque that is to be transmitted fromthe input shaft 1 a side to the input side disks 3, 3 constituting thetoroidal-type continuously variable transmission 9.

On the other hand, part of the torque transmitted through thetransmission shaft 13 to the ring gear 11 is transmitted from therespective planetary gear sets 23, 23 to the respective output sidedisks 5, 5 through the carrier 24 and first power transmission mechanism25. The torque to be applied from the output side disks 5, 5 to thetoroidal-type continuously variable transmission 9 reduces as thetransmission ratio of the toroidal-type continuously variabletransmission 9 is varied toward the speed reducing side in order tochange the whole of the continuously variable transmission apparatustoward the speed increasing side. As a result of this, in the high speedrunning operation, by reducing the torque to be input to thetoroidal-type continuously variable transmission 9, the durability ofthe composing parts of the toroidal-type continuously variabletransmission 9 can be enhanced.

Further, when rotating the output shaft 20 reversely so as to back thevehicle, the low speed and high speed clutches 31, 14 are disconnectedand, at the same time, the reversing clutch 32 is connected. As a resultof this, the ring gear 11 is fixed; and, the planetary gear sets 23, 23,while they are being in meshing engagement with the ring gear 11 and sungear 21, are rotated around the periphery of the sun gear 21. And, thesun gear 21 and output shaft 20 with the sun gear 21 fixed thereto arerotated in the opposite direction to the above-mentioned low speed andhigh speed running operations.

Next, FIGS. 13 and 14 show a more concrete example of the continuouslyvariable transmission apparatus shown in the above-mentioned FIG. 12. Bythe way, the inventors have conducted a series of tests to be discussedbelow using the continuously variable transmission apparatus shown inFIGS. 13 and 14, which have conducted us to development of the presentinvention. The present continuously variable transmission apparatuscomprises an input shaft 1 b, an output shaft 20 a, a toroidal-typecontinuously variable transmission 9 a, a planetary gear mechanism 10 a,a first power transmission mechanism 25 a, and a transmission shaft 13 aconstituting a second power transmission mechanism. Of the abovecomposing parts, the input shaft 1 b is connected to a drive source suchas an engine 15 (see FIG. 12) and can be driven or rotated by the drivesource. Also, the output shaft 20 a, which is used to take out the powerbased on the rotational movement of the input shaft 1 b, is connectedthrough a differential gear (not shown) to a wheel drive shaft.

Also, the toroidal-type continuously variable transmission 9 a is of adouble cavity type and includes trunnions 7, 7 and power rollers 4, 4each by threes in each of the two cavities, that is, a total of sixtrunnions 7 and power rollers 4. In order to construct suchtoroidal-type continuously variable transmission 9 a, a pair of inputside disks 3, 3 are respectively supported on the two end portions ofthe input shaft 1 b in such a manner that they can be rotated insynchronization with the input shaft 1 b and the respective innersurfaces 3 a, 3 a of the pair of input side disks 3, 3 are disposedopposed to each other. Of the two input side disks 3, 3, the input sidedisk 3 situated on the base end side (that is, on the drive source side;and, in FIG. 13, on the left side) of the input shaft 1 b is supportedon the input shaft 1 b through a ball spline 33 in such a manner that itcan be shifted in the axial direction of the input shaft 1 b. On theother hand, the input side disk 3 on the leading end side (that is, onthe side far from the drive source; and, in FIG. 13, on the right side)of the input shaft 1 b is fixed to the input shaft 1 b in such a mannerthat the back surface of the input side disk 3 is held by a loading nut34 while the input side disk 3 is spline engaged with the leading endportion of the input shaft 1 b.

And, on the portions of the peripheries of the middle portions of theinput shaft 1 b that exist between the pair of input side disks 3, 3,there are disposed a pair of output side disks 5, 5 in such a mannerthat the inner surfaces 5 a, 5 a of the output side disks 5, 5 arerespectively opposed to the inner surfaces 3 a, 3 a of the input sidedisks 3, 3 and the output side disks 5, 5 can be respectively rotated insynchronization with their associated input side disks 3, 3. And, thepower rollers 4, 4, which are rotatably supported on the inner surfacesof their associated trunnions 7, 7, are held by and between the innersurfaces 3 a, 3 a of the input side disks 3, 3 and the inner surfaces 5a, 5 a of the output side disks 5, 5.

In order to support these trunnions 7, 7, a frame 37 is connected andfixed to a mounting portion 36 formed in the inner surface of a casing35 by three studs 39, 39 respectively inserted through their associatedmounting holes 38, 38 formed at three positions in the outside diameterside end portion of the frame 37 and three nuts 40, 40 respectivelythreadedly engaged with their associated studs 39, 39. In theillustrated example, a gear housing 41 is fixed between the mountingportion 36 and frame 37 by these studs 39, 39 and nuts 40, 40. On theinside diameter side of the gear housing 41, an output sleeve 42 withthe two end portions thereof unevenly (projectingly and recessedly)engaged with the pair of output side disks 5, 5 is rotatably supportedby a pair of rolling bearings 43, 43; and, an output gear 44 disposed onthe outer peripheral surface of the middle portion of the output sleeve42 is stored in the interior of the gear housing 41.

Also, the frame 37 is formed in a star shape as a whole, while thediameter-direction middle portion or outside diameter side portion ofthe frame 37 is forked to thereby provide three hold portions 45, 45 atregular intervals in the circumferential direction of the frame 37. And,the middle portions of three support pieces 46, 46 are respectivelypivotally supported on the diameter-direction middle portions of theirassociated hold portions 45, 45 by their associated second pivot shafts47, 47. Each of the three support pieces 46, 46 is composed of acylinder-shaped mounting portion 48 to be disposed on the periphery ofits associated one of the second pivot shafts 47, 47, and a pair ofsupport plate portions 49, 49 which are respectively provided on andprojected from the outer peripheral surface of the mounting portion 48outwardly in the diameter direction. An angle of intersection betweenthe pair of support plate portions 49, 49 is set an angle of 120°.Therefore, the support plate portions 49, 49, which adjoin each other inthe circumferential direction of the frame 37, are parallel to eachother.

In these support plate portions 49, 49, there are formed circular holes50, 50, respectively. When the support pieces 46, 46, are respectivelyheld at their neutral positions, the circular holes 50, 50, which areformed in the support plate portions 49, 49 of the support pieces 46, 46adjoining each other in the circumferential direction of the frame 37,are concentric with each other. And, pivot shafts 8, 8, which arerespectively disposed on the two end portions of each of the trunnions7, 7, are respectively supported within their associated circular holes50, 50 by their associated radial needle roller bearings 51, 51. Theouter peripheral surfaces of outer rings 52, 52, which respectivelyconstitute their associated radial needle roller bearings 51, 51, arerespectively formed as a spherical-shaped convex surface. The outerrings 52, 52 are respectively inserted into their associated circularholes 50, 50 in such a manner that they can be prevented against shakymotion and can be swingly shifted. Also, in the support plate portions49, 49, there are formed screw holes 53, 53 respectively; and, thespherically-convex-surface-shaped leading end faces of studs 54, 54threadedly engaged into the screw holes 53, 53 are respectively buttedagainst the two end faces of the respective trunnions 7, 7. Thanks tothis structure, the shift amounts of the respective trunnions 7, 7 withrespect to the circumferential direction with the input shaft 1 b as thecenter thereof can be mechanically synchronized with each other.

On the inner surfaces of the trunnions 7, 7 supported in the interior ofthe casing 35 in the above-mentioned manner, there are supported theirassociated power rollers 4, 4 through shift shafts 55 structured suchthat the base half portions and front half portions thereof are formedeccentric to each other. Also, between the outer end faces of the powerrollers 4, 4 and the inner surfaces of the trunnions 7, 7, there arerespectively interposed thrust ball bearings 56 and thrust needle rollerbearings 57 in the order starting from the power roller 4 side. Of thesebearings, the thrust ball bearings 56 not only support thrust loads tobe applied to the power rollers 4 but also allow the power rollers 4 torotate. On the other hand, in the case of the thrust needle rollerbearings 57, in case where the composing parts of the toroidal-typecontinuously variable transmission 9 a are elastically deformed when thetoroidal-type continuously variable transmission 9 a is in operation andthus the shift shafts 55 are swung about their respective base halfportions to cause the power rollers 4 to shift in the axial direction ofthe input shaft 1 b, the thrust needle roller bearings 57 allow suchshifting motion of the power rollers 4 to be executed smoothly.

The peripheral surfaces 4 a, 4 a of the power rollers 4, 4 supported onthe inner surfaces of the trunnions 7, 7 in the above-mentioned mannerare contacted with the inner surfaces 3 a, 5 a of the input side andoutput side disks 3, 5. Also, an oil pressure type of pressing device 18a is assembled between the input shaft 1 b and the input side disk 3 onthe base end side of the input shaft 1 b to thereby secure the surfacepressure of the contact portions (traction portions) between therespective surfaces 4 a, 3 a, 5 a, so that the power transmission by thetoroidal-type continuously variable transmission 9 a can be carried outwith high efficiency.

In order to construct the pressing device 18 a, an outwardly facingflange portion 58 is fixedly disposed on the near-to-base-end portion ofthe outer peripheral surface of the input shaft 1 b and, at the sametime, a cylinder 59 is oiltight fitted with and supported by the outersurface of the above-mentioned base-end-side input side disk 3 in such amanner it projects axially from the outer surface (in FIG. 13, the leftsurface) of the present input side disk 3. The inside diameter of thecylinder 59 is small in the axial-direction middle portion thereof andlarge in the two end portions thereof; and, the present input side disk3 is oiltight fitted with the inner surface of the large-diameterportion of the leading end side of the cylinder 59 in such a manner thatit can be shifted in the axial direction. Also, in the inner peripheralsurface of the middle portion of the cylinder 59, there is formed aninwardly-facing-flange-shaped partition plate portion 60. Further,between the inner peripheral surface of the cylinder 59 and the outerperipheral surface of the input shaft 1 b, there is interposed a firstpiston member 61.

The first piston member 61 includes an outwardly-facing-flange-shapedpartition plate 63 formed on the outer peripheral surface of the middleportion of a support tube portion 62 which can be fitted with the outersurface of the input shaft 1 b; and, the outer peripheral edge of thepartition plate 63 is oiltight slidingly contacted with thesmall-diameter portion of the inner peripheral surface of the cylinder59 in such a manner that it can be shifted in the axial direction. Also,in this state, the inner peripheral edge of partition plate portion 60is oiltight slidingly contacted with the outer peripheral surface of thesupport tube portion 62 in such a manner that it can be shifted in theaxial direction. Further, between the outer peripheral surface of thebase end portion of the support tube portion 62 and the inner peripheralsurface of the base end portion of the cylinder 59, there is interposeda circular-ring-shaped second piston member 64. The second piston member64, when the base-end-side side surface thereof is contacted with theflange portion 58, can be prevented from shifting in the axial directionand, at the same time, can keep oiltight between the inner and outerperipheral edges thereof, the base end portion outer peripheral surfaceof the support tube portion 62 and the base end portion inner peripheralsurface of the cylinder 59.

Also, the cylinder 59 including the partition plate portion 60 ispressed toward the input side disk 3 by a preload spring such as acountersunk plate spring 65 which is interposed between the partitionplate portion 60 and second piston member 64. Therefore, the presentinput side disk 3 is pressed at least (that is, even in a state wherepressure oil is not introduced in the interior of the pressing device 18a) by a pressing force corresponding to the elasticity of thecountersunk spring 65, so that the input side disk 3 applies the surfacepressure corresponding to such elasticity to the contact portionsbetween the respective surfaces 4 a, 3 a, 5 a. In this case, thiselasticity is restricted to such a degree that, when a very small levelof power is transmitted by the toroidal-type continuously variabletransmission 9 a, slippage (excluding spin which is unavoidable) can beprevented from occurring in the respective contact portions between therespective surfaces 4 a, 3 a, 5 a.

Also, the oil pressure can be introduced through a center hole 66 formedin the input shaft 1 b into oil pressure chambers respectively existingbetween the second piston member 64 and partition plate portion 60 aswell as between the partition wall plate 63 and input side disk 3. Thiscenter hole 66 communicates through an oil control valve (not shown)with an oil pressure source such as a pressurizing pump (not shown).When the continuously variable transmission apparatus including thetoroidal-type continuously variable transmission 9 a is in operation,the oil pressure, which is adjusted by the oil pressure control valve inaccordance with the size of the power to be transmitted, is introducedinto the respective oil pressure chambers to thereby press the inputside disk 3, so that the surface pressure corresponding to the size ofthe above power is applied to the respective contact portions betweenthe respective surfaces 4 a, 3 a, 5 a.

Also, transmission of the rotational power to the input shaft 1 b from adrive shaft 67 communicating with a drive source such as an engine iscarried out through the flange portion 58. For this purpose, at aplurality of portions in the outer peripheral edge portion of the flangeportion 58, there are formed notches 68, 68; and, these notches 68, 68are respectively engaged with driving projecting portions 69, 69 formedin the end portion of the drive shaft 67. Also, for the above purpose,in the case of the present apparatus, an outwardly-facing-flange-shapedconnecting portion 70 is formed in the end portion of the drive shaft67, while the driving projecting portions 69, 69 are formed in thenear-to-outside-diameter end portion of one surface of the connectingportion 70.

Further, actuators 71 a, 71 b each of an oil pressure type are attachedto the respective trunnions 7, 7 so that the trunnions 7, 7 can bedriven or shifted in the axial directions of their associated pivotshaft 8, 8 respectively disposed on the two end portions of each of thetrunnions 7. Of the trunnions 7, the trunnion 7 disposed in the centralportion of the lower side of FIG. 14 can be driven or shifted throughlever arms 72, 72 in the axial directions of the pivot shafts 8, 8disposed on the two end portions thereof by a pair of actuators 71 a, 71a which are each of a single action type (that is, a type which iscapable of obtaining only the push-out direction force) and the pressingdirections of which are opposite to each other. When shifting each ofthe present trunnion 7, the pressure oil is fed only into the oilpressure chamber of one of the actuators 71 a, whereas the oil pressurechamber of the other actuator 71 a is set free. On the other hand,trunnions 7, 7 disposed on the two sides of the upper portion of FIG. 14can be driven or shifted in the axial directions of the pivot shafts 8,8 disposed on the two end portions of the trunnions 7, 7 by actuators 71b, 71 b each of a double action type (a type which is capable ofobtaining the push-out direction force or the pull-in direction force inaccordance with switching of the supply direction of the pressure oil).

A total of six trunnions 7, 7, which are disposed in the toroidal-typecontinuously variable transmission 9 a, may be shifted by the samelength in synchronization with each other by supplying the same amountof pressure oil to the actuators 71 a, 71 b using a control valve. Forthis purpose, to the end portion of a rod 73 which can be shiftedtogether with any one (in the illustrated example, in FIG. 14, thetrunnion 7 on the upper left side) of the trunnions 7, there is fixed aprecess cam 74 and the attitude of this trunnion 7 can be transmittedthrough a link arm 75 to a spool 76 of the above control valve.

The planetary gear mechanism 10 a, which is combined with theabove-structured toroidal-type continuously variable transmission 9 a,comprises a sun gear 21 a, a ring gear 11 a, and planetary gear sets 23a, 23 a. The sun gear 21 a is fixed to the input side end portion (inFIG. 13, the left end portion) of the output shaft 20 a. Therefore, theoutput shaft 20 a can be rotated as the sun gear 21 a is rotated. On theperiphery of the sun gear 21 a, there is supported the ring gear 11 a insuch a manner that it is concentric with the sun gear 21 a and can berotated. And, between the inner peripheral surface of the ring gear 11 aand the outer peripheral surface of the sun gear 21 a, there areinterposed a plurality of planetary gear sets 23 a, 23 a each setconsisting of a pair of planetary gears 22 a, 22 b combined together.Each pair of planetary gears 22 a, 22 b are meshingly engaged with eachother, the planetary gear 22 a disposed on the outside diameter side ismeshingly engaged with the ring gear 11 a, and the planetary gear 22 bdisposed on the inside diameter side is meshingly engaged with the sungear 21 a. The thus structured planetary gear sets 23 a, 23 a arerotatably supported on one side surface (in FIG. 13, the left sidesurface) of a carrier 24 a. And, the carrier 24 a is rotatably supportedon the periphery of the middle portion of the output shaft 20 a.

Also, the carrier 24 a is connected to a pair of output disks 5, 5structuring the toroidal-type continuously variable transmission 9 a bythe first power transmission mechanism 25 a in such a manner that therotational power can be transmitted between them. In order to constitutethe first power transmission mechanism 25 a, there is disposed atransmission shaft 26 a which extends in parallel to the input shaft 1 band the output shaft 20 a, and a gear 77 fixed to the one-end portion(in FIG. 13, the left end portion) of the transmission shaft 26 a. Also,on the periphery of the middle portion of the output shaft 20 a, thereis disposed a sleeve 78 in such a manner that it can be rotated; and, agear 79 supported on the outer peripheral surface of the sleeve 78 ismeshingly engaged with a gear 80 fixedly secured to the other endportion (in FIG. 13, the right end portion) of the transmission shaft 26a through an idler gear (not shown). Further, on the periphery of thesleeve 78, there is supported the carrier 24 a through acircular-ring-shaped connecting bracket 81 in such a manner that it canbe rotated in synchronization with the sleeve 78. Therefore, as theoutput side disks 5, 5 are rotated, the carrier 24 a can be rotated inthe opposite direction to the output side disks 5, 5 at the speed thatcorresponds to the numbers of teeth of the respective gears 44, 77, 79,80. Also, between the carrier 24 a and output shaft 20 a, there isinterposed a low speed clutch 31 a.

On the other hand, the input shaft 1 b and ring gear 11 a are connectedto each other through the input side disk 3 supported on the leading endportion of the input shaft 1 b and the transmission shaft 13 a disposedconcentrically with the input shaft 1 b in such a manner that therotational power can be transmitted between them. To attain this, aplurality of projecting portions 82, 82 are provided on and projectedfrom the portion of the outer surface (in FIG. 13, the right sidesurface) of the present input side disk 3, that is, the half portion ofthe present outer surface that is situated nearer to the outsidediameter of the input side disk 3 than the central portion of thepresent outer surface with respect to the diameter direction of theinput side disk 3. In the case of the present example, these projectingportions 82, 82 are respectively formed in an arc shape and are arrangedintermittently and at regular intervals on the same arc with the axis ofthe input side disk 3 as the center thereof. And, the portions, whichexist between the circumferential-direction end faces of the projectingportions 82, 82 adjoining each other in the circumferential direction ofthe input side disk 3, are formed as securing notches 83, 83.

On the other hand, on the base end portion of the transmission shaft 13a, there is disposed a transmission flange 85 through aconically-cylindrical-shaped transmission cylinder portion 84. And, inthe outer peripheral edge portion of the transmission flange 85, thereare disposed the same number of transmission projecting pieces 86, 86 asthe number of securing notches 83, 83 at regular intervals with respectto the circumferential direction of the transmission flange 85. And, thetransmission projecting pieces 86, 86 are respectively engaged withtheir associated securing notches 83, 83, thereby allowing torque to betransmitted between the input side disk 3 and transmission shaft 13 a.Since the diameter of the mutually engaged portions between thetransmission projecting pieces 86, 86 and securing notches 83, 83 issufficiently large, sufficiently large torque can be transmitted betweenthe input side disk 3 and transmission shaft 13 a.

By the way, in order that the torque to be transmitted between the inputside disk 3 and transmission shaft 13 a can be increased as much aspossible, preferably, the projecting portions 82, 82 may be provided onthe near-to-outside-diameter end portion (outer peripheral edge portion)of the outer surface of the input side disk 3. However, in the case ofthe present example, in order to secure the finishing precision of theinner surface 3 a of the input side disk 3, a flat portion 87 is formedin such portion of the outer surface of the input side disk 3 that issituated nearer to the outside diameter of the input side disk 3 thanthe projecting portions 82, 82, so that, when finishing the innersurface 3 a of the input side disk 3, the near-to-outside-diameterportion of the outer surface of the input side disk 3 can be supportedusing the flat portion 87. Also, the transmission projecting pieces 86,86 are formed such that they can be engaged into their associatedsecuring notches 83, 83 with no shaky motion between them.

Also, the leading end portion (in FIG. 13, the right end portion) of thetransmission shaft 13 a is rotatably supported on the center portion ofthe sun gear 21 a. Further, the ring gear 11 a is supported on theperiphery of the middle portion of the transmission shaft 13 a through acircular-ring-shaped connecting bracket 88 spline engaged with thetransmission shaft 13 a and through a high speed clutch 14 a (which willbe discussed later) in such a manner that the ring gear 11 a can berotated in synchronization with the transmission shaft 13 a. Therefore,while the high speed clutch 14 is connected, as the input shaft 1 b isrotated, the ring gear 11 a can be rotated together with the input shaft1 b in the same direction and at the same speed as the input shaft 1 b.

Further, between the ring gear 11 a and the fixed portion of the casing35 such as a fixed wall 89 formed within the casing 35, there isinterposed a reversing clutch 32 a. The reversing clutch 32 a, highspeed clutch 14 a and low speed clutch 31 a are all wet-type multipledisk clutches each comprising a plurality of friction plates and aplurality of separate plates which are arranged alternately. Theseclutches 32 a, 14 a and 31 a can be respectively connected ordisconnected in accordance as the pressure oil is supplied into a highspeed oil pressure cylinder 90, a low speed oil pressure cylinder 91,and a reversing oil pressure cylinder 92 which are respectively attachedto the clutches 32 a, 14 a and 31 a. Also, in case where any one ofthese clutches is connected, the connection of the remaining twoclutches is cut off. By the way, while the clutches 32 a, 14 a and 31 aare equal in the effective radius to each other, the friction plates andseparate plates are different in number from each other. That is, thenumber of the plates constituting the low speed clutch 31 a required totransmit the largest torque is set the largest (for example, eightplates each); and, the number of the plates constituting the reversingclutch 32 a and high speed clutch 31 a required to transmit relativelysmall torque is set smaller (for example, five plates each) than thenumber of the plates constituting the low speed clutch 31 a.

The above-structured continuously variable transmission apparatus issimilar in operation to the conventional structure shown in thepreviously discussed FIG. 12. That is, firstly, in the low speed runningoperation (low speed mode), the oil pressure is introduced into the lowspeed oil pressure cylinder 91 to thereby connect the low speed clutch31 a and, at the same time, oil pressures existing within the high speedand reversing oil pressure cylinders 90,92 are discharged therefrom tothereby cut off the connection of the high speed clutch 14 a andreversing clutch 32 a.

Also, in the high speed running operation (high speed mode), the oilpressure is introduced into the high speed oil pressure cylinder 90 tothereby connect the high speed clutch 14 a and, at the same time, oilpressures within the low speed and reversing oil pressure cylinders 91,92 are discharged therefrom to thereby cut off the connection of the lowspeed clutch 31 a and reversing clutch 32 a. In this state, in casewhere the input shaft 1 b is rotated, the transmission shaft 13 aserving as the second power transmission mechanism and the planetarygear mechanism 10 a transmit the rotational power from the input shaft 1b to the output shaft 20 a. In this state, by changing the transmissionratio of the toroidal-type continuously variable transmission 9 a tothereby change the revolving speeds (around the sun gear 21 a) of therespective planetary gear sets 23 a, 23 a, the transmission ratio of thewhole of the continuously variable transmission apparatus can beadjusted.

Further, when reversing the output shaft 20 a in order to back thevehicle, the oil pressures within the low speed and high speed oilpressure cylinders 90, 91 are discharged therefrom to thereby cut offthe connection of the low speed and high speed clutches 31 a, 14 a and,at the same time, the oil pressure is introduced into the reversing oilpressure cylinder 92 to thereby connect the reversing clutch 32 a. Inthis state, the sun gear 21 a and the output shaft 20 a fixed to the sungear 21 a are rotated in the opposite direction to the direction in thepreviously described low speed and high speed running operations.

In the case of the conventional continuously variable transmissionapparatus structured and operated in the above-mentioned manner,according to a study made by the present inventors, it has been foundthat, in switching the low speed and high speed modes over to eachother, the number of revolutions of the engine can vary suddenly tothereby raise a possibility of giving a driver an incongruous feeling.Also, according to the study made by the present inventors, it has alsobeen found that such sudden variation in the number of revolutions ofthe engine is caused by the following facts: that is, in the above modeswitching time, there exists a moment when the connection of the lowspeed and high speed clutches 31 a, 14 a (of course, the connection ofthe reversing clutch 32 a as well) is cut off; and, the low speed andhigh speed clutches 31 a, 14 a are different in capacity from eachother.

Now, description will be given below of this point with reference toFIGS. 15 to 17 in addition to FIG. 13.

Of the above figures, FIG. 15 shows an apparatus used in a test whichwas conducted to know not only the timing for signaling for instructingthe connection or disconnection of the low speed and high speed clutches31 a, 14 a (in FIGS. 15, 31, 14) but also the connecting states of thesetwo clutches 31 a, 14 a based on this signal. The present apparatus,using the continuously variable transmission apparatus previously shownin FIGS. 13 and 14, is used to find not only the timing for issuance ofthe signal for instructing the connection or disconnection of the highspeed and low speed clutches 14 a, 31 a, but also the timing at whichthese two clutches 14 a, 31 a are actually connected and disconnected.

By the way, the timing for connection and disconnection of the twoclutches 14 a, 31 a was judged according to the oil pressures of thehigh speed and low speed oil pressure cylinders 90, 91 which arerespectively attached to the two clutches 14 a, 31 a. That is, in casewhere the oil pressures of the high speed and low speed oil pressurecylinders 90, 91 attached to the two clutches 14 a, 31 a are low, it wasjudged that pressing pistons respectively disposed within thesecylinders are movable, there exist gaps respectively between thefriction plates and separate plates constituting these clutches, and theconnection of the present clutches is cut off. On the other hand, incase where the oil pressures of the high speed and low speed oilpressure cylinders 90, 91 attached to the two clutches 14 a, 31 a aresufficiently high, it was judged that pressing pistons respectivelydisposed within these cylinders cannot be moved, the friction plates andseparate plates constituting these clutches are contacted with eachother, and the present clutches are connected. Further, in case wherethe oil pressures of the high speed and low speed oil pressure cylinders90, 91 attached to the two clutches 14 a, 31 a are intermediate values,it was judged that the present clutches are held in a so called clutchslipping state in which they transmit the rotational power whileslipping.

Firstly, description will be given below of the test apparatus shown inFIG. 15 that is structured based on the structure of an actually usedcontinuously variable transmission apparatus. By the way, atoroidal-type continuously variable transmission 9 and a planetary gearmechanism 10 shown in FIG. 15 are similar to those previously shown inFIG. 12; and, a first power transmission mechanism 25 is also structuredsuch that sprockets 27 a, 27 b and a chain 28 are incorporated therein.With regard to reference characters, there are used the same referencecharacters as in FIG. 12 and thus the description thereof is omittedhere. By the way, although there is shown a start clutch 17 in FIG. 15,in the case of an actual test apparatus, this start clutch 17 isomitted; and, a drive source and the input shaft 1 a of thetoroidal-type continuously variable transmission 9 are connecteddirectly to each other. While a reversing clutch 32 is disposed, an oilpressure pipe is omitted; and, therefore, this reversing clutch 32 doesnot function.

As pressure oil for connecting together the high speed and low speedclutches 14, 31, there is used pressure oil which is sucked out from anoil tank 93 (in actual assembly to a vehicle, an oil pan) and is thenjetted out from a pressurizing pump 94. Between the pressurizing pump 94and the above-mentioned high speed clutch 14 {specifically, the highspeed oil pressure cylinder 90 (FIG. 13) for connecting anddisconnecting the high speed clutch 14}, there is interposed a highspeed side switch valve 95; and, similarly, between the pressurizingpump 94 and the above-mentioned low speed clutch 31 {specifically, thelow speed oil pressure cylinder 91 (FIG. 13) for connecting anddisconnecting the low speed clutch 31}, there is interposed a low speedside switch valve 96. These switch valves 95 and 96 respectively turnon/off solenoids attached thereto in accordance with a signal from acontroller 97 to thereby switch the following two modes over to eachother: that is, one mode in which the oil tanks 14, 31 are allowed tocommunicate with the jet-out port of the pressurizing pump 94; and, theother mode in which the oil tanks 14, 31 are allowed to communicate withthe oil tank 93. Also, on such portions of the oil pressure pipe thatexist between the switch valves 95, 96 and clutches 14, 31, there aremounted high speed side and low speed side pressure gauges 98, 99respectively, so that the oil pressures of the clutches 14, 31(specifically, the high speed and low speed oil pressure cylinders 90,91 for connecting and disconnecting the clutches 14, 31) can bemeasured.

The present inventors, using the above-structured test apparatus,measured not only the timing at which a signal for switching the highspeed side and low speed side switch valves 95, 96 is issued by thecontroller 97 but also the timing at which the high speed and low speedclutches 14, 31 are actually connected. The results of the measurementare shown in FIGS. 16A to 17B. FIGS. 16A to 17B respectively show notonly variations in an instruction signal given to the high speed and lowspeed clutches 14, 31 in the switching time of the low speed and highspeed modes but also variations in the connecting states of the twoclutches 31, 14. Also, of the two FIGS. 16A to 17B, FIGS. 16A and 16Bshow the variations which occur when switching the low speed mode overto the high speed mode, while FIGS. 17A and 17B show the variationsoccurring when switching the high speed mode over to the low speed mode.

Also, the horizontal axes of FIGS. 16A to 17B express the elapsed time;and, the vertical axes of FIGS. 16A and 17A express the above-mentionedinstruction signals, whereas the vertical axes of FIGS. 16B and 17Bexpress the connecting states of the clutches. By the way, theseinstruction signals are instruction signals which are transmitted fromthe controller 97 to solenoids attached to the respective switch valves96, 95 in order to control the supply of the pressure oil to the lowspeed and high speed oil pressure cylinders 91, 90 for connecting anddisconnecting the clutches 31, 14; and, the vertical axes of FIGS. 16Aand 17A show the voltages of these instruction signals. In case wherethese voltage are positive, the clutches are connected and, in casewhere they are negative, the connection of the clutches is cut off.Also, the connecting states of the clutches are expressed by themeasured values of the pressure gauges 99, 98 that are proportional tothe contact pressure ratio between the friction plates and separateplates constituting the two clutches 31, 14.

Further, solid lines shown in FIGS. 16A to 17B express theabove-mentioned variations with respect to the low speed clutch 31,whereas broken lines express the variations with respect to the highspeed clutch 14, respectively.

In the test, when switching the low speed mode and high speed mode overto each other, in both of switching directions, the instruction signalsto be applied to the switch valves 96, 95, as shown in FIGS. 16A and17A, were switched within the time of about 0.2 sec. That is, in about0.2 sec. after issuance of a signal for cutting off the connection ofthe currently connected clutch, there was issued a signal for connectingthe currently disconnected clutch. As the results of the test conductedunder these conditions, it has been found that, when switching the lowspeed mode and high speed mode over to each other, in case where thetimings for issuance of the instruction signals are set the sameregardless of the switching directions, a continuous time, during whichneither of the clutches are not connected, increases.

That is, as can be seen obviously from FIGS. 16B and 17B, in the case ofthe clutch to which a signal for cutting off the connection thereof hasbeen transmitted, the connection of the clutch is cut off in a veryshort time (see the solid line shown in FIG. 16B and the broken lineshown in FIG. 17B). On the other hand, as can also be seen obviouslyfrom FIGS. 16B and 17B, in the case of the clutch to which a signal forconnection has been transmitted, there is generated a slight time delaybetween reception of the signal and completion of the connection of theof the clutch. Also, as can be understood clearly from comparisonbetween the broken line shown in FIG. 16B and the solid line shown inFIG. 17B, the degree of the time delay varies according to the modeswitching directions.

Specifically, the time necessary for connection of the currentlydisconnected clutch (the time during which the clutch is held in theclutch-slipping state) is longer in the switching operation from thehigh speed mode to the low speed mode shown in FIG. 17B than in theswitching operation from the low speed mode to the high speed mode shownin FIG. 16B.

The present inventors not only have studied the reason for generation ofthe slight time delay between reception of the connection signal by theclutch and completion of the actual connection of the clutch and thereason for the difference of the time delay according to the modeswitching directions, but also have repeatedly conducted the test forconfirmation of these reasons. Our study and confirmation test resultshave found the following facts.

Firstly, the time delay is caused by the fact that it takes some time tocomplete the full-stroke movements of the pistons incorporated in thehigh speed and low speed oil pressure cylinders 90, 91. That is, toconnect together the friction plates and separate plates constitutingthe clutches 14, 31 in order to connect the clutches 14, 31, it isnecessary to shift the respective friction and separate plates as wellas the pressurizing pistons that are incorporated in the oil pressurecylinders 90, 91. This shifting operation is carried out by introducingpressure oil into the oil pressure cylinders 90, 91; however, due toresistance within the pipes used to introduce the pressure oil, itinevitably takes time to complete introduction of a sufficient quantityof pressure oil. This gives rise to the above-mentioned generation ofthe time delay.

Next, the reason for the different degrees of the time delay accordingto the mode switching directions is that, between the high speed clutch14 and low speed clutch 31, the strokes of the pressurizing pistonsincorporated in the oil pressure cylinders 90, 91, which are necessaryto shift the pressurizing pistons up to such positions as to allowcompletion of connection of the high speed clutch 14 and low speedclutch 31, are different.

That is, as described before, in the case of the low speed clutch 31which is required to transmit large torque, the number of the plates islarge; and, on the other hand, in the case of the high speed clutch 14which is required to transmit relatively small torque, the number of theplates is small. As the number of the plates increases, the strokes ofthe pressurizing pistons incorporated in the oil pressure cylinders 90,91, which are necessary to bring the disconnected clutches intoconnected states, increase. For this reason, as shown by the broken linein FIG. 16B and by the solid line in FIG. 17B, the time delay in theswitching operation from the high speed mode to the low speed mode (thesolid line in FIG. 17B) is larger than the time delay in the switchingoperation from the low speed mode to the high speed mode (the brokenline in FIG. 16B).

During the above time delay, since the engine serving as the powersource is not connected (or is imperfectly connected) to the drivewheel, the power cannot be transmitted from the engine to the drivewheel. To confirm the behavior that occurs in this case, the presentinventors have conducted a test for switching the low speed mode andhigh speed mode over to each other using a test apparatus shown in FIG.15. In this test, the rotation speed of an input shaft 1 a is fixed to200_(min) ⁻¹; and, any other rotary shaft was not connected to the endportion of an output shaft 20, while the output shaft 20 was set in sucha manner that it can be rotated freely. Also, in a state where the inputshaft 1 a and output shaft 20 were the same in the speed (that is, thetransmission ratio was 1), in order to switch the above two modes overto each other, the low speed clutch 31 and high speed clutch 14 wereconnected and disconnected.

And, the present inventors measured variations in the rotation speed ofthe output shaft 20 occurring due to the switching of these two modesover to each other.

As a result of this test, not only in the switching operation from thelow speed mode to the high speed mode but also in the switchingoperation from the high speed mode to the low speed mode, the rotationspeed of the output shaft 20 was lowered down (to a value lower than200_(min) ⁻¹). Specifically, however, in the switching operation fromthe low speed mode to the high speed mode, the rotation speed of theoutput shaft 20 was lowered only by 20_(min) ⁻¹ from 200_(min) ⁻¹ to180_(min) ⁻¹; and, on other hand, in the switching operation from thehigh speed mode to the low speed mode, the rotation speed of the outputshaft 20 was lowered no less than 80_(min) ⁻¹ from 200_(min) ⁻¹ to120_(min) ⁻¹. And, in either case, as the clutch was connected after theabove-mentioned time delay, the rotation speed of the output shaft 20returned back to 200_(min) ⁻¹.

Since the above test was done in a state where the output shaft 20 canbe rotated freely, in the mode switching operations, the rotation speedof the output shaft 20 was lowered. However, in an actual case, theoutput shaft 20 and the drive wheel are mechanically connected to eachother through a propeller shaft and a differential gear. Therefore, inthe mode switching operations, there is no possibility that the rotationspeed of the output shaft 20 can be lowered but, in the clutch-slippingstate, the rotation speed of the input shaft 1 a increases. For thisreason, in the mode switching operations, after the rotation speed ofthe engine serving as the drive source increases for an instantregardless of the operation of an accelerator pedal, the clutch isconnected.

An increase in the rotation speed of the engine regardless of theoperation of the accelerator pedal, even for an instant, is notpreferable because it gives a driver an incongruous feeling. Also, incase where the clutch is connected after the rotation speed of theengine increases for an instant, there is a possibility that the wholeof the power transmission system including the continuously variabletransmission apparatus can be vibrated, which also gives the driver anincongruous feeling. There is a possibility that such incongruousfeeling can increase especially in the switching operation from the highspeed mode to the low speed mode.

The present invention aims at eliminating the above-mentioned drawbacksfound in the conventional continuously variable transmission apparatus.Accordingly, it is an object of the present invention to provide acontinuously variable transmission apparatus which can reduce theabove-mentioned time delay at least in the switching operation from thehigh speed mode to the low speed mode.

Also, as another examples of a conventional toroidal-type continuouslyvariable transmission, there are known toroidal-type continuouslyvariable transmissions which are disclosed, for example, in JP-2734583and JP-A-5-39850. In each of the toroidal-type continuously variabletransmissions disclosed in these publications, between an input sidedisk and an output side disk, there are interposed a plurality of powerrollers. The power rollers are respectively supported by theirassociated trunnions in such a manner that they can be swingly rotated.When changing the rotation speed between input and output shaft, thepower rollers are swingly rotated to thereby change the rotation radiusratio of the contact point between the input side and output side disks.

In order to swing and rotate the power rollers, the trunnions arerespectively moved by a desired amount in the axial directions of therespective trunnion shafts by their respective actuators including theirrespective oil pressure pistons to thereby offset the centers ofrotation of the power rollers with respect to the centers of rotation ofthe input side and output side disks. In correspondence to the offsetamounts of the trunnions, in the contact points between the input sideand output side disks, there are generated moment forces which can swingand rotate the power rollers; and, due to such moment forces, the powerrollers are swingly rotated at an angle which corresponds to the desiredtransmission ratio.

The above actuators move the trunnions in the axial direction thereof bythe desired amount by driving their pistons using the pressure of oilwhich can be controlled by a transmission control valve. In order tostabilize the swingly rotational operations of the power rollers causedby the movements of the trunnions, for example, as disclosed inJP-A-11-294549, there is known a technique which feedbacks thetransmission control valve the shift amounts of the trunnions (the sumtotals of the swung-rotation-direction shift amounts of the trunnionsand the swung rotation angular amounts of the trunnions) by a feedbackmechanism using a precess cam.

When incorporating a toroidal-type continuously variable transmissioninto an actual vehicle, as disclosed in JP-A-10-196759, there isproposed a technique in which the toroidal-type continuously variabletransmission is combined with a planetary gear mechanism. Here, FIG. 18shows a continuously variable transmission apparatus which is referredto as a power split type of continuously variable transmission apparatusby the present inventors.

The present continuously variable transmission apparatus comprises atoroidal-type continuously variable transmission 102, a planetary gearmechanism 103, a first power transmission mechanism 104, and a secondpower transmission mechanism 105. The two kinds of power transmissionmechanisms 104, 105 are input to any two of three elements (a sun gear,a carrier, and a ring gear) of the planetary gear mechanism 103, and theremaining one element is connected to an output shaft 106 of thecontinuously variable transmission apparatus, whereby a differentialcomponent between the two elements (for example, the ring gear andcarrier) can be output to the output shaft 106.

In a low speed running mode, all of the power (torque) of an engine 107is transmitted through a drive shaft 108, toroidal-type continuouslyvariable transmission 102 and first power transmission mechanism 104 tothe output shaft 106. On the other hand, in a high speed running mode,the power of the engine 107 is transmitted through the second powertransmission mechanism 105 and planetary gear mechanism 103 to theoutput shaft 106, while part of the power is input from the planetarygear mechanism 103 to the output side disk of the toroidal-typecontinuously variable transmission 102.

The above arrangement can reduce the torque to be applied to thetoroidal-type continuously variable transmission 102 in a vehicle highspeed running operation, can enhance the durability of the respectiveparts that constitute the toroidal-type continuously variabletransmission 102, and can enhance the torque transmission efficiency ofthe whole of the continuously variable transmission apparatus.

By the way, in JP-A-11-108147, there is proposed a technique in whichthe numbers of rotations of the two elements of the planetary gearmechanism are measured and, when the numbers of rotations are almostcoincident with each other, the switching operation between the highspeed and low speed modes is executed. Also, in JP-A-9-89072, there isdisclosed a continuously variable transmission apparatus of a so calledgeared neutral type in which a toroidal-type continuously variabletransmission is combined with a single planetary gear mechanism. In thecontinuously variable transmission apparatus of a geared neutral type,in a low speed running operation, power is transmitted through thesingle planetary gear mechanism and toroidal-type continuously variabletransmission; and, in a high speed running operation, the power istransmitted only through the toroidal-type continuously variabletransmission. According to the continuously variable transmissionapparatus of a geared neutral type, there can be obtained an advantagethat, in case where, in a low-speed-side speed mode, the continuouslyvariable transmission apparatus is controlled such that a differentialcomponent of the planetary gear mechanism provides zero rotation, therecan be eliminated the need for provision of a start clutch.

However, in this type of continuously variable transmission apparatuscomprising the toroidal-type continuously variable transmission andplanetary gear mechanism combined together, in the mode switchingoperation, torque to be input to the toroidal-type continuouslyvariabletransmission varies greatly from positive to negative (or vice versa).For example, in the switching operation for switching the low speed modeover to the high speed mode, there is a possibility that the inputtorque can vary from +300 Nm to −240 Nm.

Now, FIG. 19 shows part of a power roller 4 and a trunnion 7 a used inthe toroidal-type continuously variable transmission 102. In case wherea load is applied to the toroidal-type continuously variabletransmission 102, there occurs a traction force in the axis X1 directionof the trunnion 7 a. In case where the power roller 4 is shifted, forexample, in a direction shown by an arrow mark M1 due to the tractionforce, a feedback mechanism operates in such a manner that it returnsthe power roller 4 in the opposite direction (a direction shown by anarrow mark M2).

In a radial needle roller bearing 124 for supporting the power roller 4and in a radial needle roller bearing 125 for supporting a shift shaft55, inevitably, there exist gaps. Therefore, in case where a load isapplied to the toroidal-type continuouslyvariable transmission 102 dueto the above-mentioned traction force, the power roller 4 is moved inthe axis X1 direction by the sum total amount of these gaps.

Since the power roller 4 is moved in the axis X1 direction for the abovereason, the load is applied while the transmission ratio of thetoroidal-type continuously variable transmission 102 is left fixed, thatis, without issuing a transmission instruction. In other words, in casewhere the input torque is caused to vary from 0 Nm, as shown in FIG. 20,as the input torque varies, the transmission ratio of the toroidal-typecontinuously variable transmission 102 is caused to vary, in spite ofthe fact that no transmission instruction has been issued. That is, themovement of the power roller 4 in the axis X1 direction causes sideslippage between the power roller 4 and disk, which causes the powerroller 4 to swing and rotate, thereby changing the transmission ratio ofthe toroidal-type continuously variable transmission 102.

In FIG. 20, the transmission ratio of the toroidal-type continuouslyvariable transmission 102 varies greatly in the low torque area. Thereason for this is that, in case where the power roller 4 is moved bythe above-mentioned sum total of the gaps in the low torque area, thepower roller 4 is caused to swing and rotate. FIG. 20 shows the resultsobtained from a test conducted under the conditions that thetransmission ratio was set about 0.5, the number of rotations was setconstant for about 2000, and the temperature of oil was set near to theactual temperature of a vehicle.

Now, description will be given below further of the phenomenon in whichthe transmission ratio varies mainly in the low torque area in theabove-mentioned manner with reference to FIGS. 21A, 21B and 22.

FIG. 21A shows a state of a trunnion in which a load applied to thetrunnion is zero. In this case, a pair of power rollers respectivelysupported on their associated shift shafts 55 are both situated at theirinitial positions (that is, neutral positions); and, trunnions 7 a, 7 b,following the power rollers, are also situated at their respectiveinitial positions which are (right and left) symmetric. Thus, theprecess cam 74 of the feedback mechanism is also held at its giveninitial position.

FIG. 21B shows a state of a trunnion in a light load area in which inputof the torque is started. In the light load area, since the tractionforce acts, the power rollers and trunnions 7 a, 7 b are moved in theaxial direction X1 by an amount corresponding to the above-mentionedgaps. Also, because the shift shafts 55 supporting the power rollers arerespectively held like cantilevered beams, the flexing amounts of theshift shafts 55 are also included in the moving amounts of the trunnions7 a, 7 b.

In case where the power rollers are moved in the axis X1 direction inthe above manner, there is caused side slippage between the disk andpower rollers and, in response to this, the feedback mechanism operates,so that the power rollers are finally returned to their respectiveinitial positions (neutral positions). During this operation, since thetransmission control valve has not received any transmissioninstruction, the moving amount of the transmission control valve dependsonly on the load and thus the transmission control valve little moves.Therefore, the power rollers are swingly rotated by the amountcorresponding to the moving amount of the precess cam in the axis X1direction, and the swung rotational movements of the power rollers causethe transmission ratio to vary.

FIG. 22 shows a state of a high load area. In the high load area, sincethe shift shafts 55 are flexed, the trunnions 7 a, 7 b are moved furtherin the axis X1 direction. However, in the toroidal-type continuouslyvariable transmission of a traction drive type, since the traction forceis generated by pressing the disk against the power rollers, due to suchpressing force, the trunnions 7 a, 7 b are elastically deformed in sucha manner as shown in FIG. 22 in an exaggerated manner.

With the elastic deformation of the trunnions 7 a, 7 b, the supportportions J1, J2 of each of the trunnions 7 a, 7 b move in the direction(axis X1 direction) where they approach each other. Because the movingdirection of the support portion J2 is opposite to the moving directionof the trunnion 7 a caused by the existence of the above-mentioned gap,the moving amounts of these two elements cancel each other. As a resultof this, the moving amount of the precess cam 74 in the axis X1direction is slight. For these reasons, in the high load area, therehardly occurs such swung rotation of the power roller (that is, thevariation of the transmission ratio) as occurring in the low load area.

Also, there can also be found a phenomenon in which, with a load appliedto the toroidal-type continuously variable transmission, the trunnions 7a, 7 b are elastically deformed and trunnion shafts 119 are flexed, sothat the transmission ratio of the toroidal-type continuously variabletransmission. In the toroidal-type continuously variable transmission ofa traction drive type, it is necessary to press the disk against thepower rollers and the pressing forces are supported by the trunnions 7a, 7 b. The trunnions 7 a, 7 b, as one trunnion 7 a is representativelyshown in FIG. 19, are supported by a pair of support members 49, 49which are referred to as yokes, whereby mutually-opposite-directionforces generated between the respective trunnions 7 a are allowed tocancel each other. Due to this, each of the trunnions 7 a is elasticallydeformed between the pair of support members 49, 49.

The trunnion shaft 119 itself is not deformed elastically because itdoes not receive the above pressing force; however, due to the influenceof the above-mentioned elastic deformation caused between the supportmembers 49, 49, the trunnion shaft 119 and rod 73 are swung. Due tothis, the contact point between the precess cam 74 and the cam followerof the transmission control valve is caused to vary, so that the spoolof the transmission control valve is moved in the axial direction.

As a result of this, the transmission control valve is operated togenerate the oil pressure that moves the trunnions 7 a, 7 b in the axisX1 direction, thereby changing the transmission ratio of thetoroidal-type continuously variable transmission. For example, in casewhere the precess cam 74 is moved in the axis X1 direction, the powerroller is swingly rotated by an amount corresponding to the movingamount of the precess cam 74 according to the cam lead. For instance, inthe case of the cam lead being 20 mm/360°, in case where the precess cam74 moves by 0.3 mm in the axial direction X1, the power roller isswingly rotated no less than 5.4°.

In case where these factors are combined together, as shown in FIG. 23,although no transmission instruction is issued, as the torque varies,the transmission ratio of the toroidal-type continuously variabletransmission is caused to vary. Accordingly, even in case where, asdisclosed in the above-cited publication JP-A-11-108147, the clutch isconnected when the number of rotations of the toroidal-type continuouslyvariable transmission is coincident with the number of rotations of theplanetary gear mechanism, as the torque varies, the transmission ratioof the toroidal-type continuously variable transmission is caused tovary greatly, thereby causing the number of rotations of the engine tovary.

By the way, in case where the driver judges the need for engine brakingand takes his or her foot off the accelerator, similarly to the abovecase, although no transmission instruction is issued, the torque iscaused to vary suddenly. In this case as well, the transmission ratio ofthe toroidal-type continuously variable transmission is caused to vary.However, in this case, since the engine braking is used of the driver'swill, the driver can forgive a certain degree of transmission shockcaused by such variations in the transmission ratio of the toroidal-typecontinuously variable transmission.

However, in the continuously variable transmission apparatus of theabove-mentioned power circulation type, even in case where the driverdoes not intend to switch the transmission mode, the mode is switchedinvoluntarily. Therefore, in case where even a slight degree oftransmission shock occurs in the mode switching operation, the drivefeels incongruous. That is, as in the conventional the toroidal-typecontinuously variable transmission (FIG. 23), in case where, when notransmission instruction is issued in the mode switching operation, thetransmission ratio varies greatly to thereby cause a transmission shock,the driver feels badly incongruous.

SUMMARY OF THE INVENTION

In view of the above-mentioned circumstances of the prior art, it is anobject of the invention to provide a continuously variable transmissionapparatus which can restrict the occurrence of a transmission shock inthe mode switching operation.

In attaining the above object, according to a first aspect of thepresent invention, there is provided a continuously variabletransmission apparatus comprising a toroidal-type continuously variabletransmission, a planetary gear mechanism and a clutch device, the clutchdevice comprising: a low speed clutch connected in order to increase aspeed reducing ratio and disconnected in order to decrease the speedreducing ratio; a high speed clutch connected in order to decrease thespeed reducing ratio and disconnected in order to increase the speedreducing ratio; and, a controller for switching over the connected anddisconnected states of the respective clutches to each other, thecontroller switching the transmission state of the continuously variabletransmission apparatus into any one of a low speed mode and a high speedmode by connecting any one of the clutches, wherein timings forsignaling by the controller for switching the connected and disconnectedstates of the clutches vary according to the switching directions of thelow speed and high speed modes; and, a timing for signaling forconnecting the low speed clutch with respect to the moment for signalingfor cutting off the connection of the high speed clutch in order toswitch the high speed mode over to the low speed mode is set earlierthan a timing for signaling for connecting the high speed clutch withrespect to the moment for signaling for cutting off the connection ofthe low speed clutch in order to switch the low speed mode over to thehigh speed mode.

According to a second aspect of the present invention, there is provideda continuously variable transmission apparatus, comprising: an inputshaft connected to a drive source and rotationally driven by the drivesource; an output shaft for taking out power obtained based on therotational movement of the input shaft; a toroidal-type continuouslyvariable transmission; a planetary gear mechanism; a first powertransmission mechanism for transmitting power input to the input shaftthrough the toroidal-type continuously variable transmission; a secondpower transmission mechanism for transmitting power input to the inputshaft without passing through the toroidal-type continuously variabletransmission; a controller; the planetary gear mechanism, comprising: asun gear; a ring gear disposed on the periphery of the sun gear; aplanetary gear interposed between the sun gear and the ring gear so asto be meshingly engaged with the sun gear and the ring gear; and, acarrier for supporting the planetary gear so as to be rotated, whereinthe power to be transmitted through the first power transmissionmechanism and the power to be transmitted through the second powertransmission mechanism are freely transmitted to two of the sun gear,the ring gear and the carrier, and the output shaft is connected to theremaining one of the sun gear, the ring gear and the carrier; and a modeswitching mechanism for switching the state of the power input to theinput shaft when the power is transmitted through the first and secondpower transmission mechanisms to the planetary gear mechanism, whereinthe mode switching mechanism switches over first and second modes toeach other, the first mode for transmitting the power by at least onlythe first power transmission mechanism, the second mode for transmittingthe power by both of the first and second power transmission mechanisms,the controller connects only one of clutches constituting the modeswitching mechanism to thereby set the transmission state of thecontinuously variable transmission apparatus into one of a low speedmode and a high speed mode, the low speed mode being one of the firstand second modes, the high speed mode being the other of the first andsecond modes, and timings for signaling by the controller for switchingthe connection and disconnection of the clutches vary according to theswitching directions of the low speed and high speed modes, a timing forsignaling for connecting a low speed clutch to be connected whenrealizing the low speed mode with respect to the moment for signalingfor cutting off the connection of a high speed clutch to be connectedwhen realizing the high speed mode in order to switch over the highspeed mode to the low speed mode is set earlier than a timing forsignaling for connecting the high speed clutch with respect to themoment for signaling for cutting off the connection of the low speedclutch in order to switch over the low speed mode to the high speedmode.

According to a third aspect of the present invention, there is provideda continuously variable transmission apparatus, comprising: an inputshaft connected to a drive source and rotationally driven by the drivesource; an output shaft for taking out power obtained based on therotational movement of the input shaft; a toroidal-type continuouslyvariable transmission including an input side disk, an output side disk,power rollers interposed between the input side and output side disks soas to be swingly rotatable, and trunnions for supporting the powerrollers; a transmission control valve for shifting the trunnions; afeedback mechanism for transmitting the shift amounts of the trunnionsto the transmission control valve for feedback so that a transmissionratio between the input and output disks provide a target value; aplanetary gear mechanism including three elements, that is, a sun gear,a carrier and a ring gear; a first power transmission system fortransmitting the power input to the input shaft to the output shaftthrough the toroidal-type continuously variable transmission; a secondpower transmission system for transmitting the power input to the inputshaft to the output shaft without passing through the toroidal-typecontinuously variable transmission, the power to be transmitted throughthe first power transmission system and the power to be transmittedthrough the second power transmission system being joined to two of thethree elements of the planetary gear mechanism, the remaining one of thethree elements being connected to the output shaft; a clutch mechanism,when advancing a vehicle, for switching over a first mode on the lowspeed side and a second mode on the high speed side to each other; and,a control device, when switching over the first and second modes to eachother, for controlling the transmission control valve simultaneouslywith the switching operation of the clutch mechanism within the timeduring which the clutch mechanism is switched, thereby restrictingvariations in the transmission ratio of the toroidal-type continuouslyvariable transmission.

In the above construction, it is preferable that the control device,when the clutch mechanism is switched from the first mode on the lowspeed side to the second mode on the high speed side, starts the controlof the transmission control valve later than the time when the switchingoperation of the clutch mechanism is started and completes the controlof the transmission control valve at the time when the switchingoperation of the clutch mechanism is completed; and, when the secondmode is switched over to the first mode, the control device starts thecontrol of the transmission control valve at the time when the switchingoperation of the clutch mechanism is started and completes the controlof the transmission control valve earlier than the time when theswitching operation of the clutch mechanism is completed.

According to the above-structured continuously variable transmissionapparatus of the present invention, the time delay in the mode switchingoperation from the high speed mode to the low speed mode can be reducedand an increase in the rotation speed of an engine in the mode switchingoperation can be restricted, thereby being able to reduce the degree ofan incongruous feeling that is given to the driver.

That is, since, when switching the high speed mode over to the low speedmode, the timing for signaling for connecting the low speed clutch isset earlier than the timing for signaling for cutting off the connectionof the high speed clutch, it is possible to reduce the time from thedisconnection of the high speed clutch to the connection of the lowspeed clutch.

As a result of this, in the mode switching operation from the high speedmode to the low speed mode, there can be reduced the time during whichthe high speed and low speed clutches are both disconnected, which canreduce an increase in the number of rotations of the engine in thepresent mode switching operation and thus can reduce the degree of anincongruous feeling that is given to the driver.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B are diagrammatic views of a first embodiment of acontinuously variable transmission apparatus according to the presentinvention, showing, according to the passage of time, instructionsignals to be applied to low speed and high speed clutches and theconnecting states of the respective clutches when the continuouslyvariable transmission apparatus is switched from a high speed mode to alow speed mode;

FIGS. 2A and 2B, similarly to FIGS. 1A and 1B, are diagrammatic views ofa second embodiment of a continuously variable transmission apparatusaccording to the present invention;

FIGS. 3A and 3B are diagrammatic views of the second embodiment of acontinuously variable transmission apparatus according to the presentinvention, showing, according to the passage of time, instructionsignals to be applied to low speed and high speed clutches and theconnecting states of the respective clutches when the continuouslyvariable transmission apparatus is switched from the low speed mode tothe high speed mode;

FIG. 4 is a typical view of a third embodiment of a continuouslyvariable transmission apparatus according to the present invention;

FIG. 5 is a section view of a toroidal-type continuously variabletransmission included in the continuously variable transmissionapparatus shown FIG. 4, taken along the axial direction thereof;

FIG. 6 is a section view of the toroidal-type continuously variabletransmission shown in FIG. 5, taken along the line F3-F3 shown in FIG.5;

FIG. 7 is a section view of a transmission control valve and a feedbackmechanism employed in the continuously variable transmission apparatusshown FIG. 4;

FIG. 8 is a graphical representation of the relationship between theinput torque and the operation timings of the transmission control valveof the continuously variable transmission apparatus shown FIG. 4;

FIG. 9 is a graphical representation of the relationship between theinput torque and the operation timings of the transmission control valveof a continuously variable transmission apparatus according to a fourthembodiment of the present invention;

FIG. 10 is a schematic side view of the basic structure of atoroidal-type continuously variable transmission, showing a maximumspeed reducing state thereof;

FIG. 11, similarly to FIG. 10, is a schematic side view of the basicstructure of the toroidal-type continuously variable transmission,showing a maximum speed increasing state thereof;

FIG. 12 is a schematic section view of an example of a continuouslyvariable transmission apparatus incorporating a toroidal-typecontinuously variable transmission therein;

FIG. 13 is a section view of a more concrete version of the abovetoroidal-type continuously variable transmission;

FIG. 14 is a section view taken along the line A-A shown in FIG. 13;

FIG. 15 is a circuit diagram of an apparatus used in a test conducted inthe process for developing the present invention;

FIGS. 16A and 16B are diagrammatic views of a conventional continuouslyvariable transmission apparatus, showing, according to the passage oftime, instruction signals to be applied to low speed and high speedclutches and the connecting states of the respective clutches when thecontinuously variable transmission apparatus is switched from a lowspeed mode to a high speed mode;

FIGS. 17A and 17B are diagrammatic views of the continuously variabletransmission apparatus, showing, according to the passage of time,instruction signals to be applied to low speed and high speed clutchesand the connecting states of the respective clutches when thecontinuously variable transmission apparatus is switched from the highspeed mode to the low speed mode;

FIG. 18 is a block diagram of the general structure of a continuouslyvariable transmission apparatus including a planetary gear mechanism;

FIG. 19 is a section view of power rollers and trunnions used in atoroidal-type continuously variable transmission;

FIG. 20 is a graphical representation of the relationship between theinput torque and transmission ratios of a conventional continuouslyvariable transmission apparatus;

FIG. 21A is a typical front view of a trunnion when no load is appliedthereto; and,

FIG. 21B is a typical front view of the trunnion when a load is appliedthereto;

FIG. 22 is a typical front view of the trunnion when the load appliedincreases further; and,

FIG. 23 is a graphical representation of variable widths between theinput torque and transmission ratios of a conventional continuouslyvariable transmission apparatus.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Now, FIGS. 1A and 1B show a first embodiment of a continuously variabletransmission apparatus according to the present invention. By the way,according to the present invention, there is provided a continuouslyvariable transmission apparatus in which a toroidal-type continuouslyvariable transmission and a planetary gear mechanism are combinedtogether through a clutch device including a high speed clutch and a lowspeed clutch; and, the present continuously variable transmissionapparatus is characterized in that the timings for signaling fordisconnecting and connecting the high speed and low speed clutches areimproved to thereby be able to reduce the incongruous feeling that isgenerated in the mode switching operation from the high speed mode tothe low speed mode. The structure of the present continuously variabletransmission apparatus, as a whole, is similar to the structure of thetest apparatus shown in the previously discussed FIG. 15; and, the morespecific structure of the present continuously variable transmissionapparatus is similar to that of the conventional continuously variabletransmission apparatus shown in the previously discussed FIGS. 13 and14. Therefore, the duplicate description of the specific structure ofthe present continuously variable transmission apparatus is omitted hereand description will be given below of the characteristic aspect of thepresent invention, that is, the timings for signaling for disconnectingand connecting the high speed and low speed clutches.

In the case of the present embodiment, in the mode switching operationfrom the high speed mode to the low speed mode, at the same time when asignal for cutting off the connection of the high speed clutch is issuedas shown by a broken line in FIG. 1A, a signal for connecting the lowspeed clutch is issued as shown by a solid line in FIG. 1A. Such timedelay of 0.2 seconds as shown in the previously discussed FIG. 16A isnot set in the present embodiment. Therefore, according to the presentembodiment, there can be reduced the time from such disconnected stateof the high speed clutch as shown by a broken line in FIG. 1B to suchconnected state of the low speed clutch as shown by a solid line in FIG.1B.

That is, the disconnected state continuing time t (which is shown inFIG. 1B) from the cut-off of the connection of the high speed clutch tothe connection of the low speed clutch can be reduced by the time delay(0.2 sec.) when compared with the disconnected state continuing time T(in which, as shown in FIG. 17A), the time delay (0.2 sec.) is set. Inthis manner, according to the present embodiment, in the mode switchingoperation from the high speed mode to the low speed mode, the time (thedisconnected state continuing time), during which the high speed and lowspeed clutches are both disconnected, can be reduced to thereby reducean increase in the number of rotations of the engine in the modeswitching operation, which makes it possible to reduce the degree of anincongruous feeling that is given to the driver.

By the way, in the case of the present embodiment, in the mode switchingoperation from the low speed mode to the high speed mode, as shown inthe previously described FIG. 16, there is set a time delay of about 0.2sec. between the time when a signal for cutting off the connection ofthe low speed clutch is issued and the time when a signal for connectingthe high speed clutch is issued. As described above, the time necessaryfrom issuance of the signal for connecting the high speed clutch to theactual connection of the high speed clutch is short when compared withthe low speed clutch. Therefore, in the case of the mode switchingoperation from the low speed mode to the high speed mode, even in casewhere it is controlled similarly to the previously describedconventional example, there can be reduced the degree of the incongruousfeeling that occurs in the mode switching operation.

Next, FIGS. 2A to 3B show a second embodiment of a continuously variabletransmission apparatus according to the present invention. According tothe present embodiment, the disconnected state continuing time in themode switching operation from the high speed mode to the low speed modeis shortened further than the previously described first embodiment ofthe present invention. At the same time, in the case of the presentembodiment, the disconnected state continuing time in the mode switchingoperation from the low speed mode to the high speed mode is alsoshortened further than the previously described conventional example andthe first embodiment of the present invention.

Therefore, according to the present embodiment, in the mode switchingoperation from the high speed mode to the low speed mode, a little whilebefore a signal for cutting off the connection of the high speed clutchis issued (in the present embodiment, 0.5 sec. before) as shown by abroken line in FIG. 2A, a signal for connecting the low speed clutch isissued as shown by a solid line in FIG. 2A. Therefore, in the processduring which the connection of the high speed clutch is cut off as shownby a broken line in FIG. 2B (that is, in the case of the clutch-slippingstate), as shown by a solid line in FIG. 2B, the connection of the lowspeed clutch is started (that is, the low speed clutch is turned into aclutch-slipping state). In other words, the high speed and low speedclutches are both held in the clutch-slipping state. In this state, thehigh speed and low speed clutches, while slipping, transmit torque.Therefore, according to the present embodiment, in the mode switchingoperation from the high speed mode to the low speed mode, the timeduring which the high speed and low speed clutches are both disconnected(the disconnected state continuing time) can be eliminatedsubstantially. As a result of this, an increase in the number ofrotations of the engine in the mode switching operation can be avoidedsubstantially, thereby being able to reduce greatly the incongruousfeeling given to the driver (or, thereby being able to eliminate theincongruous feeling substantially).

Also, in the case of the present embodiment, in the mode switchingoperation from the low speed mode to the high speed mode as well, alittle while (in the present embodiment, 0.3 sec.) before a signal forcutting off the connection of the low speed clutch is issued as shown bya solid line in FIG. 3A, a signal for connecting the high speed clutchis issued as shown by a broken line in FIG. 3A. Therefore, in theprocess where the connection of the low speed clutch is cut off in sucha manner as shown by a solid line in FIG. 3B (that is, in the clutchslipping state of the low speed clutch), the connection of the highspeed clutch is started as shown by a broken line in FIG. 3B (that is,the high speed clutch is turned into a clutch slipping state). In otherwords, the high speed and low speed clutches are simultaneously turnedinto their respective clutch slipping states. In this state, these twoclutches transmit torque while slipping. Therefore, according to thepresent embodiment, in the mode switching operation from the low speedmode to the high speed mode as well, there can be substantiallyeliminated the time (the disconnected state continuing time) duringwhich the high speed and low speed clutches are both disconnected. As aresult of this, in the present mode switching operation, there can besubstantially eliminated an increase in the number of rotations of theengine, which can reduce the incongruous feeling that is given to thedriver (or, can reduce the incongruous feeling substantially).

By the way, when enforcing the present embodiment, the size of the timedelay between the timings for issuance of the signals for disconnectingand connecting the respective clutches is not limited to the above valuebut it may be determined in the stage of design according to thecapacity of the high speed and low speed clutches and the resistance ofthe oil pressure pipe.

Also, description has been given heretofore of the present inventionassuming that the present invention is applied to the structures of acontinuously variable transmission apparatus of a so called split typein which the toroidal-type continuously variable transmissions 9, 9 aare combined with the planetary gear mechanisms 10, 10 a (FIGS. 12 to15); in the low speed running operation, the power is transmitted onlyby the toroidal-type continuously variable transmissions 9, 9 a; and, inthe high speed running operation, the main power is transmitted by theplanetary gear mechanisms 10, 10 a, while the transmission ratio isadjusted by the toroidal-type continuously variable transmissions 9, 9a. However, the present invention can also be applied to a continuouslyvariable transmission apparatus of a so called geared neutral type inwhich a toroidal-type continuously variable transmission is combinedwith a planetary gear mechanism, and, without switching the clutches,the reversing, stopping and advancing states can be realized. In thecase of a toroidal-type continuously variable transmission to beincorporated into such continuously variable transmission apparatus of aso called geared neutral type, incorporation of the presenttoroidal-type continuously variable transmission is effective because itcan reduce the incongruous feeling in the mode switching operation fromthe high speed to the low speed and vice versa. Further, the presentinvention can also be effectively applied to a continuously variabletransmission apparatus which, as disclosed in the above-citedpublication JP-A-2000-220729, is different from the continuouslyvariable transmission apparatus of a power split type and a gearedneutral type, comprises a toroidal-type continuously variabletransmission and a planetary gear mechanism, and switches low speed andhigh speed modes over to each other using low speed and high speedclutches.

Since the present invention is structured and can be operated in theabove-mentioned manner, the present invention can reduce the incongruousfeeling to be applied to the driver in the mode switching operation andcan contribute toward realizing a continuously variable transmissionapparatus which can provide a high efficiency through a combination of atoroidal-type continuously variable transmission with a planetary gearmechanism.

Now, description will be given below of a third embodiment of acontinuously variable transmission apparatus according to the presentinvention with reference to FIGS. 4 to 8.

A continuously variable transmission apparatus shown in FIG. 4,similarly to the continuously variable transmission apparatus shown inFIG. 18, comprises a double cavity type of half-toroidal-typecontinuously variable transmission 102, a planetary gear mechanism 103,a first power transmission mechanism 104, a second power transmissionmechanism 105, and a drive shaft 108 which can be rotated by the powerof an engine 107. The first power transmission mechanism 104 correspondsto a first power transmission system as set forth in the patent claimsof the present invention, while the second power transmission mechanism105 corresponds to a second power transmission system as set forth inthe patent claims of the present invention.

The toroidal-type continuously variable transmission 102 comprises afirst input side disk 117 a and a first output side disk 118 acooperating together in defining a first cavity 113, as well as a secondinput side disk 117 b and a second output side disk 118 b cooperatingtogether in defining a second cavity 113.

Between the first input side and output side disks 117 a and 118 a,there are interposed a pair of first power rollers 4 a and 4 b; and, theouter peripheral surfaces of the power rollers 4 a and 4 b arerespectively contacted with the traction surfaces of the first inputside and output side disks 117 a and 118 a.

And, between the second input side and output side disks 117 b and 118b, there are interposed a pair of second power rollers 4 c and 4 d; and,the outer peripheral surfaces of the power rollers 4 c and 4 d arerespectively contacted with the traction surfaces of the second inputside and output side disks 117 b and 118 b.

As shown in FIG. 6, the first power rollers 4 a and 4 b are respectivelyrotatably supported on shift shafts 55 which are respectively mounted ontheir associated first trunnions 7 a and 7 b. The second power rollers 4c and 4 d are respectively rotatably supported on shift shafts 55mounted on their associated second trunnions 7 c and 7 d (which areshown in FIG. 7).

As the trunnions 7 a and 7 b in the first cavity 113 are shownrepresentatively in FIG. 6, the trunnions 7 a-7 d respectively includetheir associated trunnion shafts 119. The trunnion shafts 119 arerespectively supported on their associated support members 49, 49. Thetrunnions 7 a-7 d not only can be moved in the axes X1 directions oftheir associated trunnion shafts 119 but also can be swung about theaxes X1, respectively.

Between the power rollers 4 a-4 d and trunnions 7 a-7 d, there areinterposed thrust ball bearings 56, respectively. Each of the thrustball bearings 56 includes an outer ring, a ball, and a thrust needleroller bearing 57. The power rollers 4 a-4 d are rotatably supported onthe trunnions 7 a-7 d by their respective thrust ball bearings 56.

As shown in FIG. 5, an input shaft 1 c is disposed so as to penetratethrough the center portions of the input side disks 117 a, 117 b andoutput side disks 118 a, 118 b. In the neighboring portion of one endportion 1 d of the input shaft 1 c, there is disposed a drive shaft 67which can be driven or rotated by a drive source such as an engine (notshown). The input shaft 1 c and drive shaft 67 are connected to eachother by a bearing in such a manner that they can be rotated withrespect to each other.

The first input side disk 117 a is mounted on the input shaft 1 c insuch a manner that it can be moved in the axis X2 direction of the inputshaft 1 c while it is prevented against rotation by a first ball spline135. Also, the second input side disk 117 b is mounted on the inputshaft 1 c in such a manner that it can be moved in the axis X2 directionof the input shaft 1 c while it is prevented against rotation by asecond ball spline 137. Therefore, the input side disks 117 a, 117 b canbe rotated integrally with the input shaft 1 c.

The output side disks 118 a, 118 b are respectively interposed betweenthe input side disks 117 a, 117 b. The first output side disk 118 a isdisposed opposed to the first input side disk 117 a, whereas the secondoutput side disk 118 b is disposed opposed to the second input side disk117 b. These output side disks 118 a, 118 b are respectively supportedon the input shaft 1 c through their associated bearings 138, 139 insuch a manner that they can be rotated with respect to the input shaft 1c. The output side disks 118 a, 118 b are connected to each otherthrough an output sleeve 42 and can be rotated in synchronization witheach other. On the output sleeve 42, there is disposed an output gear44.

On the back surface side of the first input side disk 117 a, there isdisposed a loading cam mechanism 143. The loading cam mechanism 143includes a cam disk 144 and a roller 145. The cam disk 144 is supportedon the input shaft 1 c through a rolling bearing 136 in such a mannerthat it can be rotated. In the mutually opposed portions of the cam disk144 and first input side disk 117 a, there are formed cam surfaces 146and 147 respectively; and, the roller 145 is inserted into between thecam surfaces 146 and 147.

In case where the drive shaft 67 is rotated with the roller 145 insertedbetween the cam surfaces 146 and 147, the cam disk 144 is rotated, withthe result that not only the first input side disk 117 a is pressedtoward the first output side disk 118 a but also the first input sidedisk 117 a is rotated together with the cam disk 144. Also, since thereaction force received by the cam disk 144 is applied through therolling bearing 136 to the input shaft 1 c, the second input side disk117 b is pressed toward the second output side disk 118 b.

The torque of the engine, which has been transmitted from the driveshaft 67 to the cam disk 144, rotates the input side disks 117 a and 117b, and the rotational movements of the input side disks 117 a and 117 bare transmitted through the power rollers 4 a-4 d to the output sidedisks 118 a and 118 b, thereby rotating the output gear 44.

In the above-structured half-toroidal-type continuously variabletransmission 102 of a double cavity type, in case where the inclinationangles of the power rollers 4 a, 4 b in the first cavity 113 and theinclination angles of the power rollers 4 c, 4 d in the second cavity114 are changed in synchronization with each other, the transmissionratio of the output side disks 118 a, 118 b to the input side disks 117a, 117 b can be changed.

In other words, in case where, according to the inclination angle of thepower rollers 4 a-4 d, not only the rotation radius ratio of the contactpoints between the power rollers 4 a, 4 b in the first cavity 113 andfirst input side and output side disks 117 a, 118 a is changed but alsothe rotation radius ratio of the contact points between the powerrollers 4 c, 4 d in the second cavity 114 and second input side andoutput side disks 117 b, 118 b is changed, there can be obtained adesired transmission ratio.

The trunnions 7 a, 7 b in the first cavity 113 can be respectivelyshifted in the axes X1 directions of their associated trunnion shafts119 by first actuators 161, 162 using oil pressure pistons 159 (both ofwhich are shown in FIG. 7). And, the trunnions 7 c, 7 d in the secondcavity 114 can also be respectively shifted in the axes X1 directions oftheir associated trunnion shafts 119 by second actuators 163, 164 usingoil pressure pistons 159.

Referring in more detail to this, when changing the transmission ratio,in the first cavity 113, the first trunnions 7 a, 7 b are shifted in themutually opposite directions using the first actuators 161, 162; and, inthe second cavity 114, the second trunnions 7 c, 7 d are shifted in themutually opposite directions using the second actuators 163, 164.

For example, in FIG. 7, when shifting the left-side trunnions 7 a, 7 cin the arrow mark A direction, the right-side trunnions 7 b, 7 d areshifted in the arrow mark B direction. As a result of this, theleft-side power rollers 4 a, 4 c are shifted in the arrow mark Adirection and, at the same time, the right-side power rollers 4 b, 4 dare shifted in the arrow mark B direction.

In case where the power rollers 4 a-4 d are shifted in the axis X1direction, the respective centers of rotation C of the power rollers 4a-4 d are offset with respect to the centers of rotation O (which areshown in FIG. 6) of the respective disks 117 a, 117 b, 118 a, 118 b.Thus, at the contact points between the disks 117 a, 117 b, 118 a, 118 band power rollers 4 a-4 d, according to the offset amounts, there aregenerated moment forces which rotate the power rollers 4 a-4 d in answung manner. Due to such moment forces, the power rollers 4 a-4 d arecaused to rotate swingly about the axes X1 at an angle corresponding tothe desired transmission ratio.

The actuators 161-164 can be driven by a transmission control valve 170.As shown in FIG. 7, the transmission control valve 170 is incorporatedinto a housing 171. The transmission control valve 170 comprises asleeve 173 which can be shifted in the axis direction (that is, in FIG.7, the direction shown by the arrow mark D) by a stepping motor 172, anda spool 174 which is inserted into the interior of the sleeve 173 insuch a manner that it can be moved in the axis D direction. In thesleeve 173, spool 174 and housing 171, there are formed oil passages176, 177 which, when the sleeve 173 and spool 174 are situated at theirgiven positions with respect to each other, allow an oil pressure source175 and actuators 161, 164 to communicate with each other.

On the end portion of a rod 73, which can be moved integrally with thetrunnion shaft 119 of one (7 a) of the trunnions 7 a, 7 b in the firstcavity 113, there is mounted a precess cam 74. The precess cam 74, a camfollower 191 to follow the precess cam 74 and a transmission member 195used to transmit the shifting motion of the cam follower 191 to thespool 174 of the transmission control valve 170 cooperate together inconstituting a feedback mechanism 196.

Next, description will be given below of the operation of thetransmission control valve 170 and feedback mechanism 196.

When switching the transmission state, in case where the sleeve 173 ofthe transmission control valve 170 is shifted by a desired amount in theaxis direction (in FIG. 7, the direction shown by the arrow mark D) bythe stepping motor 172 (shown in FIG. 7), the oil passage 176 of thetransmission control valve 170 is opened by a desired amount. In casewhere the oil passage 176 is opened, oil pressurized by the oil pressuresource 175 is supplied through the oil passages 177 to the actuators161-164, so that the trunnions 7 a-7 d are moved in the desireddirection (in FIG. 7, the direction shown by the arrow mark A or B).

In case where the trunnions 7 a-7 d are shifted by the desired amount inthe direction of the axis X1 of the trunnion shaft 119 in this manner,the power rollers 4 a-4 d are shifted in the axis X1 direction, so thatthe rotation centers C of the power rollers 4 a-4 d are offset withrespect to the rotation centers O (which are shown in FIG. 6) of thedisks 117 a, 117 b, 118 a, 118 b. Thus, at the contact points betweenthe disks 117 a, 117 b, 118 a, 118 b and power rollers 4 a-4 d,according to the offset amounts, there are generated moment forces whichrotate the power rollers 4 a-4 d in an swung manner. Due to such momentforces, the power rollers 4 a-4 d are caused to rotate swingly at anangle corresponding to the desired transmission ratio and, at the sametime, the trunnions 7 a-7 d are also rotated swingly in the samedirection.

In case where the trunnions 7 a-7 d are also rotated swingly in thismanner, the movement of the first trunnion 7 a is transmitted throughthe rod 73 to the precess cam 74. And, according to the position (theposition in the axial direction thereof and the position around the axisthereof) of the precess cam 74, the cam follower 191 is shifted. Thetransmission member 195 is moved by the angle that corresponds to theshifting amount of the cam follower 191, so that the spool 174 of thetransmission control valve 170 is moved in the axial direction (that is,in FIG. 7, the direction shown by the arrow mark D). That is, while theswung rotation angle of the trunnions 7 a-7 d remain unchanged, the oilpassages 176 of the transmission control valve 170 are closed to therebycut off the flow of the oil with respect to the actuators 161-164. Incase where the movements of the trunnions 7 a-7 d are feedbacked to thetransmission control valve 170 in this manner, the trunnions 7 a-7 d areshifted in the axis X1 direction and around the axis X1 by the amountthat corresponds to the shift amount of the sleeve 173 caused by thestepping motor 172.

Now, the planetary gear mechanism 103 shown in FIG. 4 comprises threeelements; that is, a sun gear 110, a carrier 111, and a ring gear 112.The sun gear 110 is fixed to the axial-direction middle portion of anoutput shaft 106. Therefore, this output 106 can be rotated as the sungear 110 is rotated. On the periphery of the sun gear 110, there isdisposed the ring gear 112 in such a manner that it is concentric withthe sun gear 110 and can be rotated independently of the sun gear 110.

Between the inner peripheral surface of the ring gear 112 and the outerperipheral surface of the sun gear 110, there are disposed a pluralityof planetary gear sets 115 (normally, three to four sets). Each of theplanetary gear sets 115 is composed of a pair of planetary gears whichare meshingly engaged with each other. In each of the planetary gearsets 115, one planetary gear is meshingly engaged with the ring gear112, while the other planetary gear is meshingly engaged with the sungear 110.

The reason for use of such planetary gear sets 115 each composed of apair of planetary gear is to set the rotation directions of the sun gear110 and ring gear 112 so as to coincide with each other. However, incase where such mutual coincidence of the rotation directions of the sungear 110 and ring gear 112 is not necessary due to the relationship withthe other composing elements of the continuously variable transmissionapparatus, the common planetary gears may also be meshingly engaged withboth of the gears 110, 112.

A pair of planetary gears constituting each of the planetary gears 115are rotatably supported by pivot shafts 116 which are disposed on thecarrier 111. The pivot shafts 116 are disposed in parallel to the outputshaft 106. The carrier 111 is fixed to a circular-pipe-shaped firsttransmission shaft 121 in such a manner that it is concentric with theshaft 121. The first transmission shaft 121 is rotatably supported onthe output shaft 106 by a rolling bearing such as a needle rollerbearing.

A transmission gear 122 is fixed to the outer peripheral surface of thefirst transmission shaft 121 through spline engagement. The transmissiongear 122 and an output gear 44 are respectively meshingly engaged withan intermediate gear 123. The transmission gear 122, output gear 44 andintermediate gear 123 cooperate together in constituting the first powertransmission mechanism 104.

The first power transmission mechanism 104 has a function to transmitthe power between the output disks 118 a, 118 b of the toroidal-typecontinuously variable transmission 102 and the carrier 111 of theplanetary gear mechanism 103. As the output disks 118 a, 118 b arerotated, the carrier 111 is rotated in the same direction as the outputdisks 118 a, 118 b at the speed that corresponds to the ratio of thenumber of teeth between the output gear 44 and transmission gear 122.

An input shaft 130 on the engine side and the ring gear 112 of theplanetary gear mechanism 103 are capable of transmitting the rotationpower thereof between them through the second power transmissionmechanism 105. The second power transmission mechanism 105 is composedof a drive gear 131 and a driven gear 132 which are meshingly engagedwith each other. The drive gear 131 is fixed to the axial-directionmiddle portion of the input shaft 130 between a start clutch 133 and aloading cam mechanism 143. The driven gear 132 is concentric with theoutput shaft 106 and can be rotated with respect to the output shaft106.

To the driven gear 132, there is fixed a second transmission shaft 134which is formed as a circular pipe. This transmission shaft 134 isrotatably supported on the output shaft 106 by a rolling bearing such asa needle roller bearing. Therefore, the driven gear 132 can be rotatedabout the output shaft 106. In the case of the present embodiment, thenumber of teeth of the drive gear 131 is set equal to the number ofteeth of the driven gear 132 so that the speed reducing ratio of thesecond power transmission mechanism 105 is set 1. For this reason, withthe rotation of the input shaft 130, the second transmission shaft 134can be rotated in the opposite direction to the input shaft 130 at thesame angular speed as the input shaft 130.

The continuously variable transmission apparatus according to thepresent embodiment comprises an oil pressure type of clutch mechanismwhich includes a low speed clutch 140, a high speed clutch 141 and areversing clutch 142. The low speed clutch 140 is interposed between thefirst transmission shaft 121 and output shaft 106. In case where the lowspeed clutch 140 is connected, the sun gear 110, ring gear 112 andplanetary gear sets 115 of the planetary gear mechanism 103 areprevented from shifting with respect to one another, whereby the sungear 110 and ring gear 112 are connected to each other through theplanetary gear sets 115. And, the high speed clutch 141 is interposedbetween the second transmission shaft 134 and ring gear 112. In casewhere the high speed clutch 141 is connected, the second transmissionshaft 134 and ring gear 112 are coupled to each other.

The reversing clutch 142 is interposed between the ring gear 112 and thefixed portion 142 a of the interior of a housing 171. In case where thereversing clutch 142 is connected, the ring gear 112 is fixed to thefixed portion 142 a of the housing 171.

The low speed clutch 140, high speed clutch 141 and reversing clutch 142are structured in the following manner: that is, they can berespectively driven by oil pressure and, when any one of the clutches isconnected by oil pressure or by an electrical control circuit, theconnection of the remaining two clutches can be cut off.

The output shaft 106 is connected to a differential gear 150 through athird power transmission mechanism 151. The third power transmissionmechanism 151 comprises a second drive gear 152 and a second driven gear153. Therefore, in case where the output shaft 106 is rotated, a pair ofleft and right drive shafts 154, 155 are rotated through the third powertransmission mechanism 151 and differential gear 150, thereby being ableto rotate the left and right drive wheels of the vehicle.

Between the transmission gear 122 of the first power transmissionmechanism 104 and the fixed portion of the housing 171, there isinterposed one-way clutch (not shown). The one-way clutch has a functionwhich not only allows the composing parts (such as the transmissionshaft 121 and transmission gear 122) of the present continuouslyvariable transmission apparatus to rotate in their respective givendirections but also prevents the composing parts from rotating in theopposite directions.

Next, description will be given below of the operation of theabove-structured planetary gear mechanism 103.

In the low speed running operation, the low speed clutch 140 isconnected, whereas the connection of the high speed clutch 141 andreversing clutch 142 is cut off. In this state, in case where the driveshaft 108 is rotated by the power of the engine 107, and also, in casewhere the start clutch 133 is connected and the input shaft 130 isthereby rotated, in the low speed running operation, only thetoroidal-type continuously variable transmission 102 is allowed totransmit the power for the following reasons.

That is, in case where the low speed clutch 140 is connected, the sungear 110, carrier 111 and ring gear 112 are coupled to one another. Thisprevents the sun gear 110, ring gear 112 and planetary gear sets 115 ofthe planetary gear mechanism 103 from rotating with respect to oneanother. Also, since the connection of the high speed clutch 141 andreversing clutch 142 is cut off, the carrier 111 is allowed to rotateregardless of the rotation speed of the driven gear 132 that is fixed tothe second transmission shaft 134.

Therefore, the rotational power of the input shaft 130 is transmittedthrough the loading cam mechanism 143 to the pair of input side disks117 a, 117 b and is further transmitted through the power rollers 4 a, 4b to the pair of output side disks 118 a, 118 b. And, the rotationalpower of these output side disks 118 a, 118 b is transmitted through theintermediate gear 123 and transmission gear 122 respectivelyconstituting the first power transmission mechanism 104 to the carrier111. In the low speed running operation, because the gears 110, 112 and115 of the planetary gear mechanism 103 are prevented from rotating withrespect to one another, the output shaft 106 coupled to the sun gear 110is allowed to rotate at the same speed as the sun gear 110 and carrier111.

In the low speed running operation, the transmission ratio of the wholeof the continuously variable transmission apparatus corresponds to thetransmission ratio of the toroidal-type continuously variabletransmission 102. Also, the torque that is input to the toroidal-typecontinuously variable transmission 102 is equal to the torque that isinput to the input shaft 130. And, in the low speed running operation,the drive gear 131 and driven gear 132 constituting the second powertransmission mechanism 105 idle respectively.

In the low speed running operation, since all of the power transmittedfrom the input shaft 130 to the output shaft 106 is allowed to passthrough the toroidal-type continuously variable transmission 102, thetransmission efficiency of the whole of the continuously variabletransmission apparatus is determined by the transmission efficiency ofthe toroidal-type continuously variable transmission 102.

Also, in the high speed running operation, the high speed clutch 141 isconnected, whereas the connection of the low speed clutch 140 andreversing clutch 142 is cut off. In this state, in case where the inputshaft 130 is rotated, the rotation power of the input shaft 130 istransmitted through the drive gear 131 and driven gear 132 respectivelyconstituting the second power transmission mechanism 105 and alsothrough the planetary gear mechanism 103 to the output shaft 106.

That is, in case where the input shaft 130 is rotated in the high speedrunning operation, the rotation power of the input shaft 130 istransmitted through the second power transmission mechanism 105 and highspeed clutch 141 to the ring gear 112, so that the ring gear 112 isrotated. The rotation power of the ring gear 112 is transmitted throughthe planetary gear sets 115 to the sun gear 110, thereby rotating theoutput shaft 106 that is fixed to the sun gear 110.

In a structure where the ring gear 112 is disposed on the input side asin the above-mentioned case, assuming that the carrier 111 stops, theplanetary gear mechanism 103 transmits the power between the ring gear112 and sun gear 110 according to the transmission ratio (a value ofless than 1) that corresponds to the teeth number ratio of the ring gear112 and sun gear 110. However, actually, since the carrier 111 rotatesinside the ring gear 112, the transmission ratio of the whole of thecontinuously variable transmission apparatus varies according to therotation speed of the carrier 111. For this reason, in case where thetransmission ratio of the toroidal-type continuously variabletransmission 102 is varied to change the rotation speed of the carrier111, the transmission ratio of the whole of the continuously variabletransmission apparatus can be changed.

In enforcing the present embodiment, in the high speed runningoperation, the carrier 111 rotates in the same direction as the ringgear 112 and sun gear 110. For this reason, the slower the rotationspeed of the carrier 111 is, the more quickly the output shaft 106disposed on the sun gear 110 rotates. For example, in case where thetoroidal-type continuously variable transmission 102 is set in themaximum speed increasing state and the rotation speed (the angularspeed) of the ring gear 112 is set equal to the rotation speed (theangular speed) of the carrier 111, the rotation speed of the ring gear112 is equal to the rotation speed of the output shaft 106. On the otherhand, in case where the rotation speed of the carrier 111 is slower thanthe rotation speed of the ring gear 112, the rotation speed of theoutput shaft 106 is faster than the rotation speed of the ring gear 112.

Therefore, in the high speed running operation, as the transmissionratio of the toroidal-type continuously variable transmission 102increases (that is, it is varied toward the speed reducing side), thetransmission ratio of the whole of the continuously variabletransmission apparatus varies toward the speed increasing side. In suchhigh speed running operation, to the toroidal-type continuously variabletransmission 102, there is input the torque not from the input sidedisks 117 a, 117 b but from the output side disks 118 a, 118 b. That is,assuming that the torque to be applied in the low speed runningoperation is positive torque, in the high speed running operation, thereis applied negative torque.

In the case of the present continuously variable transmission apparatus,the drive gear 131 of the second power transmission mechanism 105 existson the upstream side (on the engine 107 side) of the loading cammechanism 143. Therefore, in a state where the high speed clutch 141 isconnected, the torque transmitted from the engine 107 to the input shaft130 is transmitted through the second power transmission mechanism 105to the ring gear 112 of the planetary gear mechanism 103 before theloading cam mechanism 143 presses the input side disk 117 a.Accordingly, there exists little torque which is transmitted from theinput shaft 130 through the loading cam mechanism 143 to the input sidedisks 117 a, 117 b.

The torque transmitted through the second power transmission mechanism105 to the ring gear 112 of the planetary gear mechanism 103 in the highspeed running operation is in part transmitted from the planetary gearsets 115 through the carrier 111 and first power transmission mechanism104 to the output side disks 118 a, 118 b. As the speed reducing ratioof the toroidal-type continuously variable transmission 102 increases,that is, as the transmission ratio of the whole of the continuouslyvariable transmission apparatus varies toward the speed increasing side,the torque to be input from the output side disks 118 a, 118 b to thetoroidal-type continuously variable transmission 102 decreases. As aresult of this, in the high speed running operation, the torque to beinput the toroidal-type continuously variable transmission 102decreases, which makes it possible to enhance the durability of thetoroidal-type continuously variable transmission 102.

As described above, since the toroidal-type continuously variabletransmission 102 and planetary gear mechanism 103 are combined togetherto thereby constitute a continuously variable transmission apparatus ofa power circular type (a power split type), the torque to be input tothe toroidal-type continuously variable transmission 102 can becontrolled down to a low level. This can reduce the loads that areapplied to the composing parts of the toroidal-type continuouslyvariable transmission 102 such as the disks 117 a, 117 b, 118 a, 118 band power rollers 4 a-4 d which are involved with the torquetransmission, so that the durability of these parts can be securedsufficiently.

As can be seen clearly from the foregoing description, the transmissionratio of the whole of the continuously variable transmission apparatus,in the low speed running operation, varies in proportion to thetransmission ratio of the toroidal-type continuously variabletransmission 102, whereas, in the high speed running operation, itvaries in reverse proportion to the transmission ratio of thetoroidal-type continuously variable transmission 102.

Therefore, assuming that the vehicle gradually increases the speedthereof from the stopping state thereof, the transmission ratio of thetoroidal-type continuously variable transmission 102, while the lowspeed clutch 140 is being connected, gradually decreases (that is,varies toward the speed increasing side) as the speed of the vehicleincreases. And, after the high speed clutch 141 is connected, thetransmission ratio of the toroidal-type continuously variabletransmission 102 gradually increases (that is, varies toward the speedreducing side) as the speed of the vehicle increases.

That is, in the switching time for switching the low speed and highspeed running operations, the transmission ratio of the toroidal-typecontinuouslyvariable transmission 102 becomes the smallest (which showsthe maximum speed increasing state). For example, a ratio β/α betweenthe speed reducing ratio α (for example, about 2) of the first powertransmission mechanism 104 and the speed reducing ratio β (for example,about 1) of the second power transmission mechanism 105 is setsubstantially equal to the speed reducing ratio i_(H) (for example,about 0.5) of the toroidal-type continuously variable transmission 102in the maximum speed increasing time. Therefore, in the switching timefor switching the low speed and high speed running operations, thetransmission ratio of the whole of the continuously variabletransmission apparatus can be restricted from varying suddenly, so thatthe low speed and high speed running operations can be switchedsmoothly.

As described above, in the low speed mode, there is used only the firstpower transmission mechanism 104 which transmits the torque only throughthe toroidal-type continuously variable transmission 102; and,therefore, when viewed from the toroidal-type continuouslyvariabletransmission 102, the torque is transmitted from the input side to theoutput side. On the otherhand, on the high speed side, since the twopower transmission mechanisms 104, 105 are joined with the planetarygear mechanism 103, when viewed from the toroidal-type continuouslyvariable transmission 102, the torque is transmitted from the outputside to the input side; that is, there is input the negative torque.

When rotating the output shaft 106 reversely in order to back thevehicle, the connection of the low speed clutch 140 and high speedclutch 141 is cut off and also the reversing clutch 142 is connected,thereby fixing the ring gear 112. Due to this, the carrier 111 can bedriven or rotated through the toroidal-type continuously variabletransmission 102 and first power transmission mechanism 104; and, at thesame time, since the planetary gear sets 115 rotate around the sun gear110 while they are rotating about their own axes, the sun gear 110 andoutput shaft 106 are rotated in the opposite direction to the low speedand high speed running operations.

In the present embodiment, there is disposed control unit 160 which usesa microcomputer carried on board a vehicle. As will be discussed below,the control unit 160 controls a transmission control valve 170simultaneously with the speed mode switching operation to thereby beable to solve the problems found in the conventional toroidal-typecontinuously variable transmission (that is, the characteristics thereofshown in FIG. 12). That is, the control of the transmission controlvalve 170 is started simultaneously with the start of the switching ofthe clutches 140, 141 when switching the speed modes, that is,simultaneously with the start of the torque variation; and, the controlof the transmission control valve 170 is ended simultaneously with theend of the switching of the clutches 140, 141, that is, simultaneouslywith the end of the torque variation.

Specifically, when the toque starts to vary, that is, at the very momentthe clutches 140, 141 are switched, the control is started and thetransmission control is ended before the connection of the clutches 140,141 is completed. For example, as shown in FIG. 8, in the time of “3sec.” in the horizontal axis, the low speed mode clutch 140 is cut and,just before the time of “5 sec.”, the connection of the high speed modeclutch is completed. During this period, the clutches 140, 141 are beingswitched gradually.

The term “transmission control” used here means that, by driving astepping motor 172 connected to the sleeve 173 of the transmissioncontrol valve 170 as shown in FIG. 7, the sleeve 173 is moved and thusthe transmission control valve 170 is switched to thereby allow thepistons 159 of actuators 161-164 to generate differential pressure. Dueto this transmission control, the power rollers 4 a-4 d are shifted inthe vertical direction to thereby reduce variations in the transmissionratio that occur in the speed mode switching operation. Here, beforeswitching the clutches 140, 141, for example, the accelerator pedal ischecked for the opening and closing angle thereof to thereby calculatein advance the torque that would be generated after the clutches areswitched, or while reading torque variations from a previously preparedmap, the sleeve 173 is driven so that transmission control correspondingto the torque variations can be done.

In FIG. 8, torque of 300 Nm has been input from the engine to thetoroidal-type continuously variable transmission 102 and, within thetime of 3 sec. during which the switching operation of the clutches 140,141 is started, the control of the transmission control valve 170 isstarted simultaneously with the clutch switching operation. At the timewhen the clutches 140, 141 are switched to generate power circulation inthe toroidal-type continuously variable transmission 102, torque isinput into the toroidal-type continuously variable transmission 102 fromthe output disk 118 a, 118 b side and torque of −240 Nm is input ontothe input side disks 117 a, 117 b, the control of the transmissioncontrol valve 170 is ended; that is, at the time when the connection ofthe clutches 140, 141 is completed and thus the clutches 140, 141 areswitched completely, the control of the transmission control valve 170is ended.

Thanks to this, when compared with the characteristics of theconventional toroidal-type continuously variable transmission, in thetoroidal-type continuously variable transmission 102, the width of thevariations of the transmission ratio is reduced and, before and afterthe clutches are switched, the transmission ratios are almost the same.As a result of this, the number of rotations of the engine varieslittle, which makes it possible not only to prevent the engine fromincreasing suddenly in the number of rotations thereof but also toprevent the toroidal-type continuously variable transmission 102 againstvibration.

While the foregoing description relates to the switching operation forswitching the low speed mode over to the high speed mode, suchdescription can also apply similarly to the switching operation forswitching the high speed mode over to the low speed mode. In this case,by driving the sleeve 173 in the opposite direction to the abovedescription, there can be obtained a similar effect. That is, at thetime when the torque starts to vary, the control of the transmissioncontrol valve 170 is started; and, simultaneously when the torquevariation is ended or before the torque variation is ended, the controlof the transmission control valve 170 is ended. In the switchingoperation for switching the high speed mode over to the low speed mode,the torque varies, for example, from −240 Nm to 300 Nm.

Also, in the above-mentioned case, description has been given of thecase where the engine outputs positive torque. However, even in casewhere the engine outputs negative torque as in the case of enginebraking, the control of the transmission valve 170 can be carried out inaccordance with a similar concept to the above case.

By the way, as in a fourth embodiment of the present invention shown inFIG. 9, in the switching operation for switching the low speed mode overto the high speed mode, in case where the transmission control isstarted slightly after the start of the clutch switching operation, thatis, slightly after the start of the torque variation, the variationwidth in the transmission ratio of the toroidal-type continuouslyvariable transmission 102 can be restricted to a further small range.

Specifically, in the time of “3 sec.” in the horizontal axis of FIG. 9,the switching operation of the clutches is started and, slightly afterthe start of the clutch switching operation and just before the time of“4 sec.”, the above-mentioned transmission control is started. And, atthe time when the clutch switching operation is ended, the transmissioncontrol is ended. As a result of this, the variation width in thetransmission ratio of the toroidal-type continuously variabletransmission 102 can be reduced further. Therefore, according to thefourth embodiment of the present invention shown in FIG. 9, there can beobtained a better result than the third embodiment shown in FIG. 8.

In the above described embodiment, the speed mode switching operation isexecuted in about 2 seconds. However, even in case where the speed modeswitching time, that is, the clutch switching time is reduced down toe.g. 1 second or less, there can be obtained a similar effect.

Also, the present invention can also apply to a geared neutral type ofcontinuously variable transmission apparatus. In the case of a gearedneutral type of continuously variable transmission apparatus, in a firstmode on the low speed side, two power transmission systems, that is, atoroidal-type continuously variable transmission and a planetary gearmechanism are used to transmit the power; and, in a second mode on thehigh speed side, the power is transmitted only through the toroidal-typecontinuously variable transmission. In this case, in the low speed sidemode, in case where the differential component of the planetary gearmechanism taken out by the output shaft is set for zero rotation, therecan be eliminated the need for provision of a start clutch.

In a geared neutral type of continuously variable transmissionapparatus, when the toroidal-type continuously variable transmission isset on the low speed side, the first and second modes are switched overto each other. In such geared neutral type of continuously variabletransmission apparatus as well, by executing the above-mentionedtransmission control in the mode switching operation, there can beobtained a similar effect to a power circulation type of continuouslyvariable transmission apparatus.

The present invention can apply not only to a double cavity type ofcontinuously variable transmission apparatus but also to a single cavitytype of continuously variable transmission apparatus similarly. Further,the application of the present invention is not limited to acontinuously variable transmission apparatus in which two power rollerscan be disposed in each cavity, but the present invention can also applyto a continuously variable transmission apparatus in which the number ofpower rollers to be disposed in each cavity is three or more.

By the way, the present invention is effective in a continuouslyvariable transmission apparatus including two or more modes in which, inthe mode switching operation, torque passing through a toroidal-typecontinuously variable transmission is reversed, for example, in such acontinuously variable transmission apparatus as disclosed inJP-A-2000-220719 which does not include a counter shaft in the sameshaft of a combination of a toroidal-type continuously variabletransmission and several stages of planetary gears, but includes two lowspeed and high speed modes. Also, in the above-mentioned description,there is used a loading cam mechanism which is a pressing mechanism of amechanical type. However, even in case where, instead of the pressingmechanism of a mechanical type, there is used such a pressing mechanismof an oil pressure type as disclosed in JP-A-11-63146, the presentinvention can provide a similar effect.

According to the first aspect of the present invention, in acontinuously variable transmission apparatus in which a toroidal-typecontinuouslyvariable transmission and a planetary gear mechanism arecombined together, the amount of variations in a transmission ratiooccurring in the mode switching operation can be reduced and thus theoccurrence of a transmission shock can be restricted.

Also, according to the second aspect of the present invention, theamount of variations in a transmission ratio occurring in the modeswitching operation can be reduced still further.

1. A continuously variable transmission apparatus, comprising: an inputshaft connected to a drive source and rotationally driven by the drivesource; an output shaft for taking out power obtained based on therotational movement of the input shaft; a toroidal-type continuouslyvariable transmission including an input side disk, an output side disk,power rollers interposed between the input side and output side disks soas to be swingly rotatable, and trunnions for supporting the powerrollers; a transmission control valve for shifting the trunnions; afeedback mechanism for transmitting the shift amounts of the trunnionsto the transmission control valve for feedback so that a transmissionratio between the input and output disks provides a target value; aplanetary gear mechanism including three elements, that is, a sun gear,a carrier and a ring gear; a first power transmission system fortransmitting the power input to the input shaft to the output shaftthrough the toroidal-type continuously variable transmission; a secondpower transmission system for transmitting the power input to the inputshaft to the output shaft without passing through the toroidal-typecontinuously variable transmission, the power to be transmitted throughthe first power transmission system and the power to be transmittedthrough the second power transmission system being joined to two of thethree elements of the planetary gear mechanism, the remaining one of thethree elements being connected to the output shaft; a clutch mechanism,when advancing a vehicle, for switching over a first mode on the lowspeed side and a second mode on the high speed side to each other; and,a control device, when switching over the first and second modes to eachother, for controlling the transmission control valve simultaneouslywith the switching operation of the clutch mechanism within the timeduring which the clutch mechanism is switched, thereby restrictingvariations in the transmission ratio of the toroidal-type continuouslyvariable transmission.